Basement Insulation and Energy Saving

Which alternative energies and clever ideas failed my clients?

ICF and Heat Pumps.

Which future alternative energies look more promising?

1. Buying electricity from the grid when the price you pay is very low or even negative. Storing that very cheap energy, perhaps from your solar panels as well, in your electric vehicle and selling it back to the grid when it will pay you several times more.

Not as daft as it sounds with Octopus Energy offering free electricity when UK Power Networks has a surplus.

2. In the summer, heat the ground around your ground source heat pump coils so that you use a fraction of the electricity in Winter to bring heat in. I have a new page, March 2024, with more information here.

3. Heat Recovery Ventilation, solar gain and thermal mass.

The good ideas were discussed on a previous page. This page is about the bad ideas.

About a year after I wrote this, the BBC has an article about it here. They had a TV programme as well.

January 2nd 2024 I spotted another update from the BBC here. It says that air source heat pumps are getting a lot better.

The problem with stopping our use of gas is we don't have the national electricity grid we need to replace all that energy.

Heat pumps use an enormous amount of energy at peak demand. We just don't have enough. Much less have it in the right places.

At the national grid level, they won't work if we all have one.

Insulating Concrete Formwork ICF

I built with ICF for about 8 years but there are four major reasons not to use it.

It went out of shape and burst.

Insulation both sides of the concrete is just plain wrong. The concrete has thermal and energy saving benefits thrown away by insulating both sides with ICF.

All ICFs have to be filled very gently. Either you use runny concrete, which will always be porous and a basement will leak. Or, if you use any waterproof concrete it won't be waterproof because you mustn't vibrate it fully. Therefore, it will contain voids, and leak.

BS8102:2022 does not like ICF. It warns it is likely to leak and it will be difficult to fix leaks.

Tracing leaks means taking the insulation off one side at least - and throwing it and your money away. Or you could spend many thousands of pounds on internal drainage and the added costs of burying a sump (often extremely difficult) and a pump maintenance contract.

I tell you more about why you should not use ICF on another page here.

I have another page in my Answers Menu that is about WHAT WORKED for clients of mine. MHRV, the correct insulation, air tightness and thermal mass all worked when built or installed with supervision.

A statistic from an expert at a workshop 'Whole Life Carbon at the Futurebuild exhibition on March 7th 2019'

He described that in order to get data his team analysed a new home just completed by a mass national housebuilder. The SAP calculation approved by building control was a U Value of 0.16. But the actual U Value, mainly due to poor air tightness and cold bridging, was worse than 0.30.

The architects who won the Stirling prize for a passivhaus design stressed workmanship and proof the work was carried out well.

It might not matter what you choose if the building work and installation are not supervised.

Heat Pumps.

The UK and USA Governments both chose Heat Pumps as the way to reduce their country's carbon emissions. But heat pumps do not make sense.

I have been gathering evidence about heat pumps for several years, since some clients reported that after 3 years their ground source heat pump didn't work any more. Their shallow coils quickly froze their ground and it would not warm up again sufficiently over Summer to give up any heat next Winter.

A little birdy has told me that the £3.1m government grant given to Winchester University to replace gas boilers with heat pumps is going pear-shaped. It isn't producing the heat or the savings in money or carbon dioxide expected.

There is talk of litigation.

This government web page lists and provides links to the massive government funding given out under the Public Sector Decarbonisation Scheme.

I think that a lot will prove to be going wrong.

When your heat pump cannot find any heat it uses far more expensive electricity trying, hopelessly, to make you warm. But you remain cold. Sadly, that extra, expensive, electricity mostly came from fossil fuel.

I called an old client from 8 years earlier. He said that his air source heat pump ices up in very cold weather and makes heat to de-ice itself. I presume that it uses mains electricity to de-ice itself, which would mean it is using electricity but bringing zero heat inside during this process.

During March 2024 I read an academic paper from the 1990s, here. It and a visit to Futurebuild 2024 prompted me to write a new web page here. I learned that when a ground source heat pump freezes the ground around the pipework, that if and when that soil is able to thaw out, the water can separate and rise to the surface causing the soil to settle, they said 22%, damaging and putting the GSHP pipework out of action.

A new client in December 2022 turns out to have worked in the energy industry for many years including a time as the manager of a gas-fired power station.

He was trying to help me understand how the wholesale price of electricity was influenced by many variables and how the variable wholesale price affected the economics of a heat pump.

It really isn't simple. I tried a few times to explain it but he kept saying I got it wrong. Therefore, I have collected his emails together into one pdf document that you can read here.

The point of this little lesson in the economics of generating electricity is to illustrate why every 1kWh hour of electricity from fossil fuels costs about 2kWh of fossil fuel, if from gas, which most Winter electricity will be for some time yet.

That means twice the carbon dioxide produced for each kWh of electricity compared to each kWh burned in a gas boiler.

Apparently, even if we had loads more wind turbines than we do now, that power wouldn't all be used by us to power our heat pumps without using fossil fuel. Wind generated electricity has to be shared with Europe because .... open the .pdf above and try to make sense of it, if you need to. (In part, because even if we shut all our gas fired power stations and relied heavily on solar and wind, if it suddenly got cloudy or the wind temporarily dropped, we would have to be connected to gas fired power stations in Europe to keep us going till the sun came out or the wind picked up.)

What these facts mean are that if you have a heat pump, which will obviously be powered by electricity from the grid, then your heat pump needs to deliver at least two units of energy from the heat source for every one unit of electricity from the grid before you even get close to saving any carbon. Before you get close to the carbon efficiency of a gas boiler. But the financial cost to the homeowner is even greater. The retail cost of 1kWh of gas is 10p. The retail cost of 1kWh of electricity is 34p (December 2022 with UK government subsidy).

1kWh of electricity costs 3.4 times 1kWh of gas.

The first 3.4 of the efficiency of a heat pump is only catching up to equal the cost of gas. But when you want most heat, when your ground is already cold or the air is cold outside, no heat pump will come close to matching the cost to run a gas boiler. Your heat pump will be wasting you money and the extra electricity requires burning more fossil fuel and harming the planet more than a gas boiler.

Heat pump systems come with a figure for CoP. Coefficient of Performance. I just looked through the Screwfix web site and found a Samsung heat pump with a SAP Seasonal Efficiency 469%, which I am assuming means a CoP of about 4.7. It is rated A+++.

But my client is explaining that 4.7 is really only 2.35 compared to the original gas. Your gas boiler might be almost 100% efficient. Heat from gas costs 10p per kWh. The heat pump with SoP of 4.7 requires 0.21kWh of electricity so 1kWh of heat costs 7p.

But only while the CoP is 4.7.

You might still think that is useful, and no doubt 'Seasonal Efficiency' has taken some cold days into account as well as warm days.

But does it fully take into account the fact that your heat pump is used far, far more when it is cold outside, and much, much less when it is warm outside? I don't think so.

What effect does cold air outside have on an Air Source Heat Pump?

We can learn a lot from a lengthy study into Ground Source Heat Pumps where the heat is obtained from boreholes. I provide a full reference and more information lower down. For now, let us study figure 3.

Within only 3 or 4 days the heat extracted from the boreholes dropped significantly. The heat obtained for the same amount of electricity was already less. The CoP had dropped significantly. After 60 days the drop was as much again and after 120 days the temperature of the refrigerant coming out had dropped about 40% from the start before any heat had been extracted.

For the same amount of grid electricity to power the system, the CoP dropped 40% over a season.

Clearly then, an air source heat pump CoP would also drop as the air temperature dropped outside throughout Autumn then Winter.

I conclude:

Ground Source Heat Pumps cost more to get the same heat further into the cold season.

Ground Source Heat Pumps cost more each year after the soil they took heat from fails to warm up again fully over the Summer.

Air Source Heat Pumps are absolutely hopeless at heating your home efficiently when it is near freezing outside.

Do you know when your heating is on the most?

My guess is that most households require half their annual heat in just the coldest two weeks a year.

A search on Google found opinions that if the air outside is less than 40°F, which is 5°C, air source heat pumps struggle.

But that is when we want most heat.

Below -5°C ASHPs can use immense amounts of electricity but fail to bring any heat into your home at all.

                ( Someone has told me that air source heat pumps have got an electric heater hidden inside. When the unit realises
                its efficiency is less than one, it switches off the heat pump and turns on the electric heater instead. When it is really cold,
                you are spending 3.4 times the cost of gas and producing twice the carbon dioxide compared to a gas boiler.)

Our coldest 2 weeks each year are somewhere between the two.

Another of my clients was told that his new house needed a single phase electricity supply - until he mentioned his ASHP which, he was told, meant he needed 3 phase. Single phase supplies something like 23kW maximum continually. If he needs 3 phase, someone thinks his house will need in excess of 23kW continually for the ASHP to work full blast trying to get some heat when the air is freezing outside.

If every home required 3 phase instead of single phase because they bought a heat pump, would the grid cope?

How many of these homes would freeze during a power cut?

Any figure for CoP from a sales person or supplier is likely to be at or about best possible case.

An Air Source Heat Pump requires hardly any electricity if you want your home at 20°C and it is 18°C outside. It is easy to refrigerate some heat from 18°C.

But if you want a lot of heat when the air is freezing outside, it takes a lot of electricity from the grid to freeze the air still further to get some heat from it.

Most of the time your ASHP is working hard its CoP might be very low or even negative. You will probably use more electricity sometimes than the heat you get out.

You will use more electricity, than you would have used gas with a gas boiler, and that electricity cost 3.4 times more than gas.

And the electricity is producing twice the carbon dioxide compared to a gas boiler because gas fired power stations are only 50% efficient.

In the summer an ASHP, or in a new borehole a GSHP, your heat pumps might both have a CoP of 5 and deliver you 25 units from the original 10 units of gas. BUT THIS IS ONLY WHEN YOU DON'T WANT ANY HEAT.

On a freezing cold day when you want the most heat from your ASHP, or if your GSHP is trying to get heat from a borehole 10 years old (your shallow GSHP coils failed years ago), your heat pump CoP might drop to 1.8 and you will only get 9 units of heat energy for your home from the 10 units of gas that generated the electricity. Overall, from start to finish and over the long-term, a heat pump is usually less efficient or effective than a gas boiler.

Click on this image to read this guy's tweet.

The academic paper, below, proves that GSHP loses efficiency over the season and over the years as well. Which means you pay increasingly more as the months and years go by for the same amount of heat.

It is also, therefore, proof that an ASHP will be far less efficient on colder days.

Air Source Heat Pumps are worse for the planet than gas, until we no longer generate electricity from fossil fuels. Until we can generate a huge surplus of electricity with no carbon emissions, ASHPs will make us burn more gas than we would without them.

Ground Source Heat Pumps will never achieve a return on investment and in time they will require more electricity than the value of the heat they get from the ground.
- Shallow coils beneath our garden will only be efficient for one Winter at best, then completely fail in 3 years or less.
- Boreholes, thousands of metres deep, will deteriorate from day one eventually failing completely in a couple of decades or so.

Electricity is energy in a form we call electrons. Other forms are chemical, radiant, mechanical, thermal and nuclear. They can all be converted into another. Electrons have no size or mass. They are just energy and every atom in every molecule throughout the universe is surrounded with electrons.

That means all the earth beneath our feet is full of electrons.

What we think of electricity is a flow of these electrons through material. Copper wire is a very good material. The flow is not one electron travelling miles and miles but each electron nudging a neighbour and taking its place, until our light bulb or our heat pump is working.

The proportion of energy from the sun that we prevent hitting the earth and generate electricity with instead is incredibly small.

If we generate a surplus of electricity from solar and wind and dissipate that surplus by grounding it to earth, it makes no difference to the earth that would have coped with that same energy hitting it directly from the sun.

But, as far as I can tell, we need a huge surplus of energy from solar, wind and tide (a lot of which we can waste dissipating the surplus to earth) if we are to have enough electricity without burning fossil fuel even when it is dark at night, the wind drops or the tide turns.

That means many, many times more alternative energy than we produce now.

Until then we need to continue burning fossil fuel.

What the typical sales person tells you about the efficiency of Air Source and Ground Source Heat Pumps is probably mostly untrue.

As is proven on this web page, these technologies do not work when the air outside is cold or the buried pipework made the ground cold.

The gas required to generate the electricity to power a heat pump greatly exceeds the heat brought in over a heat pump's lifetime.

Heat Pumps are bad for you and bad for the planet.

However .....

We often hear in the news that the big problem is our being unable to store the rich supply of solar energy in the Summer to use in the Winter.

Photovoltaics on our roofs generate the most when we don't need it.

We can only store a small amount in batteries.

BUT THERE IS HUGE POTENTIAL TO STORE THE SUN'S SUMMER ENERGY IN THE GROUND AS HEAT.

If we heated water on our roofs and pumped that heat into the ground alongside our shallow Ground Source Heat Pump coils, then if we pump in more heat throughout the Summer than we will require throughout the Winter, our shallow GSHP system will always be super efficient.

Imagine the difference in costs.

During the snow in December 2022, electricity is 34p per kWh and gas 10p per kWh, after UK government subsidy.

According to Ofgem, the average British household has 2.4 people living in it and uses 2,900 kWh of electricity and 12,000 kWh of gas annually. This works out at 242 kWh of electricity and 1,000 kWh of gas per month.

I am going to presume that gas is mainly used in the Winter, and that 3,000kWh are used during the coldest month.

That much gas costs £300.

If a heat pump used a third that much power to deliver the same heat, the electricity would cost £340.

But if a heat pump with a cold heat source used the same power as the heat it got out the electricity would cost £1,020.

What if we used only £50 of electricity over the Summer to pump 10,000kWh of heat into the ground surrounding our shallow GSHP coils, and our GSHP only needed a tenth the electricity to get it out during January because, while the air was freezing outside, the ground around our pipes was still warmer than we wanted our home to be inside?

To get 3,000kWh with a CoP of 10 would require 300kWh of electricity costing £102, plus our £50 over the summer = £152.

Our £50 over the Summer would be completely carbon-emission-free, because we would only pump heat when the sun was shining which is when other people's photovoltaic panels are generating all the electricity we need.

And, actually, that makes me think it must be possible to have lots of solar water heater panels on your roof and just one photovoltaic panel.

When the sun shines and the photovoltaic generates enough electricity, the pump will turn on and flush the heat out of the other panels and put it in the ground.

Obviously an investment is required, but this needn't be connected to the mains at all. Completely independent, free and automatic to run.

Relying on a heat pump during a power cut could mean freezing to death for some. Perhaps the single photovoltaic, or a petrol generator, could operate the ground source heat pump temporarily and just enough if the ground source was still quite warm.

STES.

This technology first caught my attention in 2018. Seasonal Thermal Energy Storage. STES.

Icax Promotes pumping heat into the ground beside GSHP coils.

There is an academic exploring a similar idea. A chartered engineer and chartered geologist, she is a research fellow whose blog describes her excitement at the idea. Two of her blog pages here: testing and monitoring.

Beware.

Two other considerations before you sink a deep borehole to store energy as heat.

First, if you find water, your heat will be washed away.

Second, if you and your neighbour both drill boreholes quite close to each other, you might get a dispute over one accusing the other of stealing his heat.

Link to the academic paper, mentioned above, about the longer term effects of Ground Source Heat Pumps.

This is the source page

and this is the .pdf I downloaded from it.

These tables are also copied and pasted from the .pdf.

very clear deterioration over 15 years.

Between a and c you see the recovery of heat after heat extraction for one year.

between b and d you see that after 15 years the soil clearly starts each cold season colder than previously, and comparing b to a, after 15 years heat extraction is clearly less efficient.

		Shallow GSHP pipe being buried 2m deep.
		A GSHP borehole being drilled.
		A client's heat pump installation in Buckinghamshire. I kid you not. He said he went over his £50,000 budget.
		A client's GSHP and, on the right, water heating comprising a hot water tank with an air source heat pump on top. Instead of his ASHP bringing heat in from the air outside, this client has Mechanical Heat Recovery Ventilation and after the air on its way outside has given some heat up to the air coming in, that air, which is still warmer than the air outside, gives up more heat to the ASHP and that heat heats their domestic hot water. They seemed to think it worked.

This article about living with a heat pump was published by Homebuilding and Renovating June 2022.

I have copied and pasted it because it might disappear from their web site. I have omitted the images and adverts.

He does not tell us that his heat pump remained efficient on the coldest days. Yet he must know that is a big concern for many.

But, very usefully, he does explain the scope of the necessary works.

What is it Really Like to Live With a Heat Pump?

Energy expert David Hilton installed an air source heat pump three years ago, a decision which gives him confidence the technology could suit most UK homes

Heat pumps have been heralded as the future of home heating, but while there are a lot of people telling us how great heat pumps are, not as many people are telling homeowners what it's actually like to live with one.

Air source heat pumps and ground source heat pumps come with a variety of pros and cons, much as gas boilers do, and choosing to opt for a heat pump is a bold decision. It can require quite significant research and preparation, but specified in the right way, they have potential to make your home cheaper and more carbon-friendly to run in the long term.

I installed a heat pump three years ago, and from the initial decision-making process to installation to adapting to the way your home is heated, this is what it's like to live with one.

We had been living in our home for nine years with an oil fired central heating system.

We are not rural, but at the time when our home was built in the 1980s our little development was equipped with electrical storage heaters. Over the years many of these homes were subsequently fitted with a wet central heating system and oil or LPG gas boilers. Ours was one such property.

When, as a family, we started to outgrow the property we went through the motions of evaluating whether it would be better to move to a bigger property or extend the existing one. Building an extension won, and as the project moved through the design stage we realised very quickly that the oil boiler would simply not be good enough for our newly enlarged home.

The other issue was that the boiler flue protruded through a wall where the new lounge would be, and the new lounge would block the route to the oil tank for refilling. If we were to keep an oil boiler then the boiler position and the tank position would need to move. These were both not easy options so what was the alternative? Yes, an air source heat pump.

Getting Our Home Ready For a Heat Pump

An air source heat pump moves heat from the air outside to your home. The water flow temperatures in the central heating circuit are a lot lower than you have with a boiler, therefore the emitters often need to be increased or you need to have underfloor heating installed.

To make an air source heat pump run efficiently you need to optimise the efficiency of the home as well, so the design stage of the project received a new injection of detail.

We looked at ways to improve our insulation and make the property more draught proof. The central heating system was inspected to make sure that the radiators were big enough for much lower flow temperatures, and that the pipework was big enough to carry enough heat.

If you have a microbore pipe (10mm - 12mm, it does not matter if it is copper or plastic) then a heat pump system can really struggle to deliver the heat. Oversized circulation pumps can be used to overcome the resistance but then there could be additional noise in the pipes, unbalanced emitters and lower efficiency due to pump power consumption.

How We Chose Our Air Source Heat Pump

The emitters were all acceptable and a heat loss calculation was done to determine the size of heat pump required. It came back at around 8kW so we selected a heat pump of around 11kW to cover the heat load when it is very cold outside.

The choice of heat pumps available is increasing every day, and there are a number of things that differentiate between different air source heat pump products.

First you have the choice of monobloc or split. A monobloc has the refrigeration plant in the box outside the property and the unit is connected back to the home via water pipes and electrical wiring. There is no refrigerant pipe. A split system has half the heat pump outside and half inside the home, with the two bits connected via a refrigerant pipe.

Monobloc units are the most common air source heat pumps in England, and that is what we chose.

Two issues I was slightly concerned about was that the outdoor fan unit may be a bit noisy in our garden, or that it had been designed to only supply heat to the central heating. As it was, the hot water is provided by a second heat pump built into the hot water cylinder, and receives air from the exhaust of the heat recovery ventilation systems. It might sound complicated but in real terms it's not: the set-up essentially comprises two different heat pumps with different refrigerant gas that behave in different ways.

The outdoor unit could potentially supply the hot water as well but we did not want it to run in summer, and we wanted to use the waste heat in the stale air in the ventilation system.

We did not want to have the outdoor heat pump run in summer because even though we have close neighbours, and it passed the noise test for planning permission, we were still sensitive that it might disturb them when all the windows are open in the summer. As it happened this unit is really quiet and we need not have worried.

How Easy Was Installation?

The ductwork for the hot water heat pump was the most tricky thing to install, but the rest of the installation went very smoothly. A solid base was built for the outside unit and the pipework was installed as new parts of the extension were completed. We then changed all the Thermostatic Radiator Valves for wireless motorised valves to provide accurate room-by-room thermostatic control.

How Has My Home Heating Changed?

We’ve had the heat pump for three years now, and there are a number of things that we have had to get used to. The radiators no longer become radiant hot, for example. You can hold them and you won't get burned.

The flow temperature was initially set at 48°C and dropped a few degrees in mild weather. As we got used to the system we lowered the flow temperature to 38°C and it drops to around 28°C in milder weather. You do have to get used to the fact that the heat has a much slower reaction time. As the reaction time is slower, more careful room control is required.

The different zones (rooms) are set on a schedule to not all come on at once, and we stagger the times when the rooms call for heat, thus reducing the load on the heat pump. The heat is gentle. Whether it is the rooms with underfloor heating or radiators they are all sized to run at the same temperature so they all operate on the same circuit.

As the reaction time is slower, more careful room control is required. The stored water temperature in the hot water cylinder is lower than it would be with a boiler - you would expect the water to be around 60°C to 70<°C with a boiler, but a heat pump does not like to make that type of heat and many cannot get to that level without the use of a back-up electrical heater.

The temperature of a shower is around 38°C so it doesn't really matter that the water is stored at a lower temperature of around 50°C because you can use a bit more water from the cylinder and mix in less cold. This does mean, however, that you will have a slightly larger cylinder than if you had a boiler. Our cylinder is 300L rather than a 250L boiler option, but considering that Building Regulations now require your water to be no more than 48°C at the tap, the lower store temperature will make no difference.

Has the Heat Pump Been Cheaper to Run?

Initially the air source heat pump was more expensive to run than the oil boiler, but when you factor in that oil was really cheap several years ago, and we had not really got to grips with the nuances of living with a heat pump, the pendulum soon swung the other way.

Oil was 34p per litre when we put in the heat pump. You get 10 kWh per litre so that is around 4p per kWh when you factor in the boiler efficiency.

Electricity was 12p per kWh and the heat pump was only 250% efficient (when measured in the house not at the heat pump) meaning that it cost around 5p per kWh.

Now electricity is 28p per kWh so each unit of heat costs 11p but oil is now around £1 per litre so when you factor in the efficiency the cost is about the same. But, we have solar PV panels so quite a lot of the electricity, especially in the summer, is free.

What Else Did I Notice?

The heat pump has never been a noise nuisance and the temperature in the home has always been comfortable, even when there was a load of snow outside. It is, however, imperative to get the heat pump designed and installed by experienced installers who understand your home, your expectations and most of all the working habits of the heat pump.

In the three years since installing the heat pump the technology has moved on, and the new refrigerant gasses and better software - as well as our experience of having a heat pump solution in a 1980s renovated property - fill me with confidence that air source heat pumps can indeed be a successful long-term solution for most UK homes.

David Hilton

David is a renewables and ventilation installer, with over 35 years experience, and is a long-standing contributor to Homebuilding and Renovating magazine. He is a member of the Gas Safe Register, has a Masters degree in Sustainable Architecture, and is an authority in sustainable building and energy efficiency, with extensive knowledge in building fabrics, heat recovery ventilation, renewables, and also conventional heating systems. He is also a speaker at the Homebuilding & Renovating Show.

Passionate about healthy, efficient homes, he is director of Heat and Energy Ltd. He works with architects, builders, self builders and renovators, and designs and project manages the installation of ventilation and heating systems to achieve the most energy efficient and cost effective outcome for every home.

A few clients, over the years, mentioned storing summer heat in a water tank in their basement to partly heat cold water in winter before that water reached their boiler. But it always seemed a problem insulating that tank well enough for it to really work well.

Modern Methods of Construction MMC.

There is a lot of talk about improving the quality of house building by building homes in factories and delivering them in panel form and erecting them on site.

But, during 2022 these factories seem to have been closing faster than they were opening.

I can see a lot of benefits, especially workmanship, but the sadness is that panels will be lightweight and have no thermal mass. These homes could need more heat on the coldest days and more cooling on the hottest days than my preferred choice using concrete and thermal mass.

In the UK, only about 1.5% of our emissions are from producing cement while 28% are from heating our homes. If we halved the 28% by doubling the 1.5% so everyone evened out their home temperature with thermal mass, it would be a net reduction of about a third for both added together. Except that the savings from thermal mass would continue many years after we stopped using cement to create it.

Profit from photovoltaic panels yourself.

When I looked into photovoltaic panels and a bank of batteries purely and solely for charging fully electric cars, and not connected to any house wiring or the grid, it looked very profitable. Especially if you sold energy to other car owners during sunny weather when you could generate more than the capacity of your battery bank.

More information and some maths behind Wind Turbines.

In this short video, a BBC correspondent explains quite clearly why domestic wind turbines are sadly a waste of money.

A wind turbine with a radius of 1m captures energy from wind over about 3m².

A wind turbine with a radius of 2m captures energy from wind over about 11m².

A wind turbine with a radius of 25m captures energy from wind over about 1570m².

A wind turbine with a radius of 50m captures energy from wind over about 6300m².

You would need more than 2,100 1m radius wind turbines on houses to match the electricity generated by one large turbine in the North Sea.

20 times higher mast 572 times as much electricity.

This is why wind turbines are in the North Sea and on hillsides, not on every house. They are a waste of time on a house.

Iron is melted to extract the rust from ore.
Iron is melted again to extract the oxygen from rust.
Iron is melted again to produce steel.

It is very easy, when extolling the virtues of alternative energy, to forget that the iron used to make the kit was mined in Australia and it took a huge amount of coal and water to firstly remove the rust from the rock, second to purify the rust into iron and third to turn iron into steel. It required oil to power the transport around the world. The same for the copper pipes, the plastics, the aluminium and the copper wiring. We use a huge amount of energy and water to turn earth resources into manufactured products. Buying kit used a lot of water, created pollution and increased global warming. Changing a component or throwing the whole thing away and replacing it creates even more.

A slide from a presentation at Futurebuild.

basement insulation thermal mass

On April 24th 2019 the Futurebuild people made a number of the presentations at their March exhibition available for free online. You might have to register here.
Some of the information on this page is from the presentation: "The Value of Energy Positive Buildings".
The slide above is from the presentation: "Lark Rise Energy Project".

It is a fact that our electricity suppliers can pay 3 times as much for wholesale electricity at 5.30pm as they paid 45 minutes earlier before we got home and switched everything on.

It is likely that we will soon have to pay 3 times more for early evening electricity compared to mid-afternoon electricity. So it must make sense to face our photovoltaic panels at where the sun is when we want electricity.

When we are charged a different rate throughout the day for electricity, some will charge up batteries from the grid when the price is near zero (this might be because solar panels or wind turbines are generating more than we can use mid-afternoon). Perhaps their bank of batteries will be in their electric car. They just plug it in.

Then, only 2 hours later, they will sell excess electricity from their car to the grid when they get paid, let's say, 30p per kWh. No panels involved. Just a mobile phone app.

Taking a shower or rinsing washing up under a hot tap is pouring expensive energy down the drain. Consider showering in the bath with the plug in. Don't drain the bath before the water cooled and you kept the heat.

Cavity Wall Insulation.

Another gem of a simple idea from my happy MHRV customer.

He put his cavity wall insulation in himself. He has blockwork inside and outside that is 50mm of rockwool then 150mm of insulation board, such as Celotex, QuinnTherm or Recticel, then his cavity then his brick.

He explained that the rockwool follows the contours of his blockwork, ensures no air gap between the blockwork and his rigid board and ensures that joints in his rigid board are closed by rockwool.

Going Green and having the opposite effect.

The experts at the Futurebuild workshop discussed the high carbon cost of materials and equipment as well as energy. Apparently, specifying up to 8 times the equipment needed is not uncommon. Neither is it uncommon to completely replace a whole unit instead of replacing just the part that failed. This all wastes carbon emissions and precious water along the supply chain.

They went on to explain that sourcing all the building materials and all the materials your equipment is made from, as well as all the transportation; and the end of life costs in removing and replacing anything all add up toward your Whole Life Carbon. A concrete office block completely gutted and refitted when a new tenant moves in and then demolished after only 10 years to be replaced by an even bigger concrete tower, is a terrible waste of carbon.

One of the expert's teams had to quantify the carbon in a new public building. They found that a lot of the timber was Canadian but it had been sold and moved to Southern USA before being purchased and transported to Britain. The total carbon was more than twice Scottish timber that only travelled 300 miles or so. In comparison, how far would your concrete travel? The aggregate, 77% by weight, might be quarried where they batch the concrete. If so usually a maximum of only 20 miles. The cement: a 15th of your concrete might have come from Port Talbot and another 15th from Greece. Another 15th is the water that only travelled as far as the truck. Overall, concrete is greener than many suppose.

Some of the best results the experts at the workshop got anywhere were concrete used where its useful life would be expected to exceed 150 years - which could be your house. The carbon investment in a concrete house becomes insignificant annually if it will be in use unchanged for 150 years.

Another cause of carbon waste the experts were keen to make clear was the effect on Whole Life Carbon designing a building and its services to fully meet the demands for energy during the coldest and the hottest times.

The experts said that in order for every building in the land to get enough mains energy for air conditioning during the hottest few hours a year and full-bore heating during the coldest few hours a year, the extra national grid infrastructure and extra building equipment and services and energy certain to cope are twice what is required on the other 363 days a year.

They impressed upon us that if our buildings can only cope with 95% the peak demand during the coldest and hottest few hours a year, then the total Whole Life Carbon for everything required (mains supply infrastructure, equipment and energy) is halved.

And the way to smooth out the need for peak energy is thermal mass.

One of the experts said that his Victorian, London home, refurbished to maximise thermal mass, air tightness, insulation outside and heat recovery ventilation maxed at 25^oC throughout the heat wave last year. A new build could do even better.

I Googled MHRV and looked at Images. This was first page. Your MHRV supplier might well try to supply you with an average one air change per hour with ducting to every room. But will this be too much when everyone is out or asleep?

And will he tell you to put your equipment out of reach?

The exhibitor at the HB&R Show I spoke to was angry that MHRV would not work after the first couple of years because filters weren't being changed.

About 25 years ago, the Building Research Establishment, BRE, produced a paper about the U value of a basement without insulation.

The U Value of an average domestic basement, just because it is buried, is about 0.16 before you add any insulation.

The point, therefore, is that a basement neither needs much insulation nor much heating.

You cannot include a figure for 'cave' in your SAP calculation. You can include a figure for thermal mass. You can include a larger figure for thermal mass by including the soil. In this way, the soil surrounding a buried basement is insulation, even if you aren't allowed to actually call it insulation.


Click on each image to open full size images in new tabs.

Fabric First Approach.

Continuous insulation outside the thermal mass walls and floors. Shown here in yellow. Minimum 2 metres of soil between the basement floor slab and the outside air.

A Chinese manufacturer, Himin, can make a roof entirely of solar panels. You needn't have a roof with panels fixed to it. Just one roof of panels. Other manufacturers make photo voltaic roof tiles.

I am making the assumption that solar panels might not be completely weatherproof so my waterproof roof is the flat roof above the bedrooms.

At most times, a rise in temperature from solar gain, cooking, heating, washing and body heat is stored in the concrete until released during the night resulting in less heating required first thing in the morning.

You might only need a 1 KW plug-in electric heater on a timer and timed to use the cheapest electricity to make a difference to the whole house before you wake up.

The benefit of the concrete house is its air-tightness and thermal mass. Once up to temperature, you hardly need anything to keep it there because of cooking, washing and your own body heat.

The environmental benefit of concrete is not in how much renewable energy you get from an investment of tens of thousands of pounds, but how much less energy you use during its incredibly long life time than building any other way.

Can a concrete house be zero carbon over its lifetime?

What have we learned so far?

The simple ideas work best.

First and foremost, good workmanship - which might require continuous, effective inspection to refuse to accept anything sub standard - works a lot better than rushed work and sub standard materials.

Note the quotation at the top of the page about the mass built house designed to 0.16 but built to worse than 0.30 by a national house builder.

And the other note that the builder was required to prove all his work was carried out well"

The academics concluded that
- insulation, air tightness, solar gain and thermal mass;
- as well as equipment sufficient to keep us completely comfortable only 95% of the time;
- that would all last many, many years;
- without dragging materials from half way around the world;
are all the right direction.

I cannot see that we can be zero carbon without generating something that we give to the grid as well as using very little energy ourselves.

Ofgem tells us that the average home uses 14,900kWh of energy from the grids each year.

Our first task must be to use a lot less. Build with supervision and wise choices so that you waste less throughout the lifetime of the dwelling.

Our second task is to use less equipment and make the equipment last longer. If you use less energy by wasting less, you should require less equipment.

Third, take some clothes off instead of air conditioning on the 5 hottest days of the year. Put on a jumper or two instead of more heating on the coldest 5 days of the year.

Our fourth task, which currently seems to be the hardest, is to contribute our excess solar energy we generated to others.

Selling energy to the grid is ruinously unprofitable. Charging up EVs to replace more petrol and diesel might be the better route.

How much energy might be needed to produce the cement to build a concrete house with a basement that requires virtually zero heat from the grids to keep comfortable?

6,000kWh

Compared to 14,900kWh used annually by the average home.

According to a number of web sites, including The International Energy Agency, the UK's cement required 116kWh to produce each tonne.

This simple spreadsheet cement needed.xlsx concludes that cement needed to build the structure of a standard new self build home, 12m x 8m internally over 3 floors including a basement, would require cement with a cost of about 6,000kWh.

The spreadsheet is not protected and you can change it, so I obviously cannot be responsible for something you may have changed.

One last crazy idea.

The problem with any heat pump is the extra electricity you need when the source heat gets colder.

When it was -5°C during December 2022 your mains water did not freeze. Your mains water was still about 10°C.

It would be cheaper, it would require less electricity and would create less carbon dioxide if we were using a heat pump to remove heat from our tap water rather than a frozen borehole or freezing air outside.

WE ALL HAVE TWO HEAT PUMPS IN OUR HOMES ALREADY,

We all have a fridge and a freezer.

From my power station client,

"If we found somewhere to put 5 chest freezers in our homes, and we filled them all with water from the tap, the latent heat in the freezing process is about 100kWh per m3 of water."

A commercial chest freezer holds about 2.5m³ and would give up 250kWh every time we filled it and froze the water.

If we require 3,000kWh during the coldest month we need to freeze, empty and refill that freezer 12 times over the month. Or we could have a smaller freezer we emptied more often.

Before humans had freezers they stored winter ice in big holes in the ground and preserved meat and fish well into the summer - because the soil is a very good insulator (which is why ground source is generally a bad idea).

Instead of preserving fish alongside your ice in a hole, you could have pipework that, instead of air conditioning, cools your house on hot days. Slowly melting the ice to cool your home.

So far so good. At first this seems like a good idea.

But, if everyone did this, the water company might have a water shortage. And if all the ice was put down a sewer outside it might freeze and block the sewer.

12 times 2.5m³ = 30m³, which weighs 30 tonnes. Equivalent to 100 trolleys in a supermarket filled with bottles of milk.

You couldn't chip 30 tonnes of ice out of a freezer without destroying the freezer.

You couldn't carry and lift 30 tonnes of water in and out of of your freezer, and then outside, in one month without doing yourself an injury and losing all your heat because your front door is open.

But maybe someone, somewhere, has the space to have a warehouse freezer that they can wheel 10 supermarket trolleys full of milk bottles full of tap water in quite easily, and wheel them outside easily and quickly when they are frozen. With another 90 trolleys all set up and ready to take their turn.

But we still lose 50% efficiency if the electricity was produced from gas or coal.

Perhaps that someone could store the ice until summer and use it to cool their home instead of air conditioning? This is when the ice is thawed ready to use again next year.

As is always the case, if the ice could easily be wheeled into an underground store, it would be kept as ice more cheaply than in any insulated building above ground.

If you want to save energy and reduce CO₂, you must avoid filling your home with clever kit that requires immense amounts of energy and water to produce the steel and copper but doesn't save anything on the hottest or coldest days each year, you must make sure your architect finds a sensible place for your MHRV unit and of course you need to insulate, reduce draughts and avoid over heating in summer.

And work probably needs to be supervised if you don't have the work carried out by the most reliable person you know - yourself.

I am convinced that once built and lived in, my proposed home, maximising thermal mass and solar gain with air tightness, insulation and MHRV, would require the least energy to make the kit and to keep the dwelling warm and cool compared to any other scheme. Read about it here MHRV, the correct insulation, air tightness and thermal mass all worked.

You might not like any of my thinking. Fair enough. I'm not selling it. I'm only sharing it.

Phil Sacre
2018, 2019, 2020, 2021, 2022 and 2023.

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