Cavity Insulation - better than expected

[OG]

We've just had our first gas bill (for heating and cooking) since the cavity wall insulation was installed mid-December.

Last winter (Nov 07- Mar 08) - average daily usage 10 units per day This winter (Dec 08 - Mar 09) - average daily usage 7 units per day !

I didn't expect it would make that much difference, and I'd say that this has probably been a colder winter than last year.

I reckon that means we should pay back the (70% subsidised) cost in about 15 months.

[ransley]

How did temperature days units compare, a bill is meaningless without knowing temp heating days. So i say it was warmer this year.

[OG]

Oh good, if you've got (Dec, Jan, Feb) temperature stats for (07-08) and (08-09) for Liverpool I'd be really interested to see them.

[OG]

Thanks for the head up - I've not come across temp heating days before, but I found a definition on Wikipedia and the monthly stats for Liverpool on Weather Underground

Weather Heating days (monthly Sums base 65) Dec 07: 661, Dec 08: 744 Jan 08: 622, Jan 09: 805 Feb 08: 649, Feb 08: 676

Average Mean daily Temperatures Dec 07: 5C, Dec 08: 4C Jan 08: 7C, Jan 09: 3C Feb 08: 5C, Feb 08: 4C

So it looks to this novice like it /has/ been colder this year.

[Peter Scott]

I can't give any figures of my own because I've had cavity insulation for a long time in various houses. However I think the saving might well be better than the raw heat leakage figures. Our sensation of warmth is determined by the temeperature of the walls not the air in the room. ISTR that this is called Prevost's Theory of Exchanges or somesuch. Objects in a container exchange radiated heat with the walls not the air. When you insulate, the temperature of the walls goes up and very likely you can have a lower room air temperature and still feel warm. It's also why when you get home from holiday it takes a while before you feel warm even after the air is warmed. Or is it just that you've been baking on the beach?

Anyway it's great to be saving money and energy. Just put another 10cm in the loft and you'll be turning the heating off altogether!

Peter Scott

[ARWadsworth]

Coldest winter for 13 years.

cavity wall insulation has paid for itself in less than12 months. My quick payback time is due to the low price I paid for the installation, the way my house is constructed (not normal bricks), having a gable end that is exposed to the Pennines and the price increases of gas.

Cavity wall insulation usually take 2 to 4 years payback time.

Adam

[David Hansen]

On Tue, 10 Mar 2009 08:33:53 +0000 someone who may be Peter Scott wrote this:-

Not quite. How warm people feel depends on a number of factors which do include radiation from objects (including walls) but also include air temperature, air velocity, the occupants themselves and what they are doing.

That is indeed a factor in lower air temperatures being possible without affecting comfort..

[Mike Clarke]

Possibly a bit longer, hopefully we might manage to get some warm weather in the summer when the heating won't be needed anyway. So it might take 15 winter type months for payback, but still a good return.