Heat Loss

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If you have thermostatically controlled heating in your home, and most of us do, then your boiler will be controlled by the temperature measured in a heat lossparticular area in your home i.e. where the thermostat is placed! Regardless of how well insulated you home is the boiler will burn fuel and supply heat to your radiators until the temperature set on this thermostat is reached, before switching itself off. This does not mean that all of the rooms in the house are at the main thermostat temperature, their temperature will be dependent on the heat loss from the room, the radiator heat output of each room and the individual radiator thermostat (if you have them fitted). So the more you can do the reduce heat loss from your home the more rapidly the desired temperature will be reached and the earlier the boiler will switch off, ultimately reducing the amount of fuel you burn and amount you pay.

This is all fairly obvious, what is less easy to determine is what you should look at first to reduce heat loss, which will be the most cost effective for you, and how much should you look to invest to get a sensible return on your investment.

Where is the heat loss?

Some of the areas where heat is lost in the average home, with some of these contributing much more to overall heat loss than others are as follows, Roof/loft; The walls; The floor; The windows; Gaps in the doors; Air vents **; Clothes Dryer; Vents; Fire places; Attic hatch.  The percentage heat loss attributed to various areas of your house is usually quoted by most commentators on the subject, the numbers generally accepted are :-

The roof 25%
The walls 35%
Floor 15%
Doors and Drafts 15%
Windows 10%

**Please note that some air vents are important for your health!






As an observation a percentage is not a helpful way to consider heat loss, since no matter how well your house is insulated ultimately all the heat will eventually dissipate from the property, given that it is cooler outside.    It is more instructive to consider how much energy each insulation measure will save and to calculate how much money that will save depending on the fuel you are burning to keep warm, and then to calculate a payback time for any investment you have made.  Throughout this section this is the method used.

Relatively old un-insulated houses (perhaps 1930’s) are used as examples in this section of the site, since newer houses are likely to have insulation pre installed.   Two sizes have been chose, a 3 bed and a 5 bed house; clearly a 4 bed house will lie in the middle somewhere.  Keeping each of these warm for most of the year given that they have no effective insulation installed will use approximately 20,000 kWh of energy for the three bed house and for the larger house about 30,000 kWh.  The table below shows how much this energy costs with several fuel source options.

House size Estimated energy use to
heat house for a year
Electric (Std) Economy 7
LPG Fuel Oil
3 bed 20,000 kWh £ 960 £ 3080 £ 1500 £ 1160 £ 860
5 bed 30,000 kWh £ 1440 £ 4620 £ 2250 £ 1740 £ 1290

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0 # data after insulationMichelle Spaul 2013-09-03 16:54
Really useful site. With the example above I wonder what the heating costs for the two example properties would be after insulation?
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0 # Cost of EnergyMartin Winlow 2013-05-25 08:40
Hi,Whilst useful, your article really needs to add a reference to the time the costs were calculated at. With NG having increased in price nearly 3-fold in the last 10 years the cost comparison chart is almost worthless. Better still add a chart comparing the *change* in cost by fuel type. That in itself would be very illuminating.Re gards, MW.
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0 # replyRichard 2013-05-25 20:32

When we first started this website in 2008, the first thing we thought was that it would all go out of date very quickly. So we spent a lot of time scripting all of the calculations on the site so that with one price variable file update all the prices on the site change. We do this once a year. So all the prices on the site are pretty much up to date and the site is current, this is stated all over the place on the site. The same logic applies to equipment, many prices here have reduced and these are also updated in the same way.

There is a bit of a trend analysis here (you'll have to copy the link)

confusedaboutenergy.co.uk/.../ ...

but it is a work in progress and more will follow when time allows. Any thing specific you want to see?


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0 # Eco7Martin Winlow 2013-05-26 18:07
Hi - Thanks for the response. I note your comments about the figures being up to date and that this is 'all over the site'. Perhaps, but if it isn't on the page I was looking at and I don't look at any other pages, how am I supposed to know?

Anyway , reading your reply I note you are using a fairly average 'normal' electricity cost rather than Eco7 rates which are fully one third of the figure you gave for electricity cost. Perhaps this needs a mention too? I use a thermal store which 'charges' on Eco7 electric and 'discharges' throughout the day to UFH and hot water. Were it bigger I could comfortably run the whole house off it, all year round.

It would make for a very competitive and efficient system and will, I suspect come to be much cheaper than the fossil fuel options in a fairly short time frame.

Regar ds, MW.
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0 # replyrichard 2013-05-26 19:02

Su nday, 26 May 2013 19:02

Thanks for getting back.

I take your point. At the top of each appropriate article I have made it much clearer (the prices used that is) regarding EC7 the two article below do some calcs on that.

confusedaboutenergy.co.uk/.../ ...
confusedaboutenergy.co.uk/.../ ...

The rate we use for EC7 is higher however in the site, it is about 7p per kWh here are all our prices

confusedaboutenergy.co.uk/.../ ...

It is fairly comprehensive, but there are some omissions.

T he reason we use 7p is that in reality for most users the cost averages out higher than the actual EC7 rate used at night, since the very act of having EC7 means that your standard tariff is quite a lot higher. In an unlikely situation where you used electricity only at night during the EC7 hours then our rate is too high.

I think you are right regarding EC7 and Fossil fuels especially for those using LPG and OIL that EC7 is competitive. Another site user would suggest to yo that you just use standard tariff and switch every year to get a lower tariff then you only need to buy cheap heaters, so no major central heating costs. In your case it must be worth considering switching regularly at least.

Final ly and to be utterly pedantic, electricity is 80% fossil fuel generated in the UK.


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0 # Estimated energy use to heat house for a year.Billy Knight 2012-04-10 10:08
What is the assumption of hours per day in the above table to output those figures?
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0 # Heat lossRichard 2012-04-10 13:09
The numbers in the article are not based on hours use per day, but on the average energy consumption per year for that type of property. The values are based on various government reports. and of course each year varies so they are also based around averaging over a number of years. In the cold winter of 2010/11 our heating bill went up 20%. If you want to look at your own situation it would be best just to look at the number of kWhs that you consume and scale the cost accordingly. The government has a vast resource of data freely available at:- www.decc.gov.uk
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0 # attic insulationLaurence Lacey 2012-03-09 20:30
If I apply too much attic fibreglass, my attic water tank freezes up.
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0 # attic insulationRichard 2012-03-10 14:41
Now thats a pain in the neck, can you insulate arround the tank
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0 # loft tankspip gas and oil 2012-03-16 12:23
Insulate around but not under the tank. Be sure that your tank is on wood planks or plywood, not chipboard, as any condensation on it (or leaks) will destroy chipboard. All pipes in an insulated loft need a minimum of 25mm thick lagging, not the 15mm DIY stuff.
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0 # Solid Wall InsulationMax 2012-01-23 15:04
I was surprised not to see any guidance on this topic, given that through the wall heat loss is apparently such a high percentage, and that not all properties have a cavity in the wall.
Given that those properties that don't are probably loosing an even higher percentage by this route how does applying external, or internal, solid wall insulation stack up economically.
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0 # Solid Wall InsulationRichard 2012-01-23 20:24
good point, will investigate.
c heers
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+1 # Heat losspip gas and oil 2012-03-16 12:17
This has been a bone of contention for years. If you have cavity walls you have has 25 years of free or subsidised insulation but if you have solid, which are, of course much worse at retaining heat, there has never been ANY grants.
I have put this to Norwich CC and the Energy saving Trust several times but it falls on stony ground.

My opinion is that ALL the grants should be removed now from cavity and put into solid wall exterior cladding.
Inte rior cladding is cheaper but beset with vapour barrier pitfalls.
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