ConfusedAboutEnergy.co.uk

Cavity wall insulation


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I had originally just used your 4000 Kwh as an average houshold should save. This caused great excitement as local gas prices are 12p/Kwh which meant we would save £480PA. This seemed too good to be true and of course it was. Our annual bill is £1500 but taking out the standing charges and estimated gas usage for hot water we were left with £822 as a good estimate of what portion of the bill is actually heating. This equates to a possible £164 PA @ 20% saving due to cavity insulation which I think is more realistic. This is still a substantial saving and awaiting quotations to calculate possible payback period. I was quite suprised to see that we use on average less than half the energy consumption for a 3 bed house than your estimator is using.

This is a comment on "Loft Insulation"

Comments (1)

Hi Jeff
It is amazing the variations, last month we had someone write in to say they were using 33,000 kWh per year to heat their three bed bungalow. You are using less than 9000kWh for heating and yes 20% of this corresponds to about £200 at your charge rate.

In the article we state this:-

*Calculations assume the energy required to heat an un-insulated 3 bed house is 20000 kWh
(assumptions are here: http://www.confusedaboutenergy.co.uk/index.php/heat-loss-and-insulation/heat-loss)

Uninsulated is the key word here. If you already have loft insulation and double glazing the proportional effect of adding cavity wall insulation will be lessened, the heat flow through the wall remaining static and being governed by thermal gradient and wall materials.

From you email, do you live in Jersey? 12p per kWh for gas, wow, is it really that much! Is it LPG?

the 20000kWh number comes from UK averages, and includes all climates by the way.

would you consider putting you data on our survey?

http://www.confusedaboutenergy.co.uk/index.php/the-real-house-survey

cheers

Richard

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Household Energy Costs

Site Guidance

All calculations on this site are based on current fuel prices they are checked regularly are automatically updated and were last changed on:-
19^th February 2013
For complete clarity, all calculation using current fuel prices are coloured red.

The costs calculated based on these fuel prices should be regarded as 'good estimates', given that fuel prices vary in different parts of the county and at different time of the year.

The calculations also have different levels of accuracy depending on the nature of the calculation. For example calculating the energy use of a known power output TV is very easy compared to calculating the effect on energy savings when insulating a cavity wall.

Site Units

The main units used in this site are in the table below, For a complete explanation of any of these Wikipedia is an excellent resource.

Unit	Name	Detail
W	Watt	Unit of Power
kW	Kilowatt	1000 watts
kWh	Kilowatt hour	Measure of Energy
L	Litre	Measure of Volume

Best Investment table

Measures to reduce fuel bills		ROI*
	Lagging	1
	Loft Insulation	1.9
	Cavity Wall Insulation	2.2
	Underfloor Insulation	4.2
	Solid Wall Insulation	15.1
	Solar Hot Water	34
	Double Glazing	55.6
*ROI is the time it takes in years to return the investment in fuel savings for an average gas heated 3 bed semi-detached house. The table assumes no government incentive schemes are used.

Renewable Energy Measures		ROI**
	Heat Pumps - Replacing Electric	4 to 8
	Heat Pumps - Replacing LPG	15 to 30
	Wind Power	14 to 55
	Solar Photovoltaics	24 to 64
**ROI is the time it takes in years to return the investment in electricity savings. The table assumes no government incentive schemes are used.