Cavity Wall Insulation

ROI
2.2-Years

If you have cavities in your walls which are not already filled with insulation then you have a great opportunity to save quite a lot of money. Most household heat is lost through the walls and anything to slow this down helps. The story is similar to loft insulation, you can reduce your energy bill for heating by up to 25%, but again more realistically 20%. The table below calculates the effect of only insulating your cavities considering several main household fuels and estimates a payback time for the investment. For a larger house cavity wall insulation will cost £ 500 and for the smaller house about £ 350.

	Approx % energy saving	Approx energy saving per year	Gas	Electric (Std)	Economy 7	LPG	Fuel Oil
3 bed house	20%	4000 kWh	£ 180	£ 580	£ 292	£ 308	£ 264
Payback time with cavity wall insulation costing £ 400 (3 bed house)			2.2 years	0.7 years	1.4 years	1.3 years	1.5 years
5 bed house	20%	6000 kWh	£ 270	£ 870	£ 438	£ 462	£ 396
Payback time with cavity wall insulation costing £ 550 (5 bed house)			2 years	0.6 years	1.3 years	1.2 years	1.4 years
Calculations assume the energy required to heat an un-insulated 3 bed house is 20000 kWh and a 5 bed house is 30000kWh.

Is it worth doing?

Yes. This measure is on a par with insulating the loft as one of the most effective thing you can do to your house to save money and protect the environment. And like loft insulation there are grants available to many of us to completely pay for the insulation, check for grants from the warm front scheme (this is now gone), energy companies and local authorities and check with your local energy advice centre.

Comments (6)

Average U-value for cavity wall insulation? and what would you say is the average payback time for houses in general then?

While I would agree generally that cavity wall insulation is a good thing please point out that it isn't appropriate for all properties. Houses that are exposed to wind driven rain, such as those on the west coast of the UK, may end up with significant problems from having cavity wall insulation. The rain is driven into the cavity and soaks the filling this can cause damp and condensation problems internally as well as then freezing and causing problems with external rendering etc.

So generally a good thing but not always. It is a shame that it is pushed so hard without consideration being given to the site and exposure to extreme weather that a property may have.

As my wife would say to me "you are a sad and lonely man, I pity you".... Who said that then?????
I can honestly say I never have a dull moment, but thanks for the concern and your kind comment regarding the site! My latest endevour is an app for android phones on energy. good fun! don't worry I do drink beer and other more normal stuff.

thank you whoever made this website. It is very helpful. But you have no life- why do this for fun

Thanks justin, looks useful.

Hi - you can quickly and easily apply for insulation grants by going to http://www.insulationgrants.info. As your article rightly says, this can save you hundreds of pounds off your energy bill and help to create a more energy efficient home.

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	pence	lowest priority
	£ 10+	Think twice, perhaps you should focus elsewhere first
	£ 100+	Worth doing
	£ 1000+	Focus your effort here to save as much money as possible

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

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.

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