Insulation for solid walls

[thomas.rynne]

I have just removed the chimney breast from the rear of my victorian terrace and noticed that even though there is no real cavity there is a gap of about an inch. I'm about to brick up the whole left by the chimney breast but wondered if there is anything I can put in the small cavity to improve the insulation.

On a related point, I have been browsing the web trying to find out how to improve the insulation of solid walls. There is plently of general advice -it sounds like the best option is external insulation- but I can't find a company who actually supply the materials required or a company which will install external insulation.

Does anyone have experience with this? I live in Aldershot, Hampshire.

Considering the number of houses in the UK with solid walls it is surprisingly hard to persue this option. Loft insulation and cavity wall insulation seem to get all the attention. I suppose these approaches have a better return on investment, but I can't see all the victorian houses being demolished any time soon so I would expect to find more companies offering solutions.

thanks Thomas

[Phil L]

No, anything less than 50mm is useless where CWI is concerned.

There are plenty of them, Millfold are one of the better ones:

> Does anyone have experience with this? I live in Aldershot, Hampshire. >

It's a lot more expensive than normal CWI, so much so that it will never turn a profit - you will never save as much as it has cost for installing, also your house has to be rendered, something that is fast turning prospective homebuyers off.

[JupiterJon]

External insulation is a possibility but in my similar age property I intend to insulate the walls-without-windows internally and put double glazing in the walls with windows (sash box removal). This leaves the existing sash box and nice appearance and while not perfect shoudl be much better than oringally. The rooms are reasonably large in my case and it can be done room by room. One thing I know I will have to be careful with in ssealing between the cold wall and the now warmer wall to prevent condensation. There may be better ways.

2p Jon

[thomas.rynne]

You mean the return is less than mortgage interest rates? As long as the return is higher than this wont it pay for itself eventually. Also, if fuel prices rise wont the pay back time reduce?

thanks Thomas

[meow2222]

sounds suspiciously like a cavity to me.

The original reason for these cavities was to keep out damp, mainly in coastal areas. If the outer leaf got wet the inner would stay dry.

Applying insulation on the surface works as well, and you can put a lot more there, but of course its not as cheap.

Insulation on the interior keeps the outside looking good, but loses the temp stabilising effect of the masonry's thermal capacity. It also means replastering. Outside insulation means rendering over it. The general best bet is internal insulation at the front, maintaining good appearance, and exterior insulation elsewhere.

Materials for solid insulation are not hard to come by, I wonder if youre just not sure what to get.

NT

[Phil L]

Conventional CWI takes decades to pay for itself, exterior insulation takes much longer, because A) It costs more, and B) It's not as effective.

That's not to say it shouldn't be installed - the house will be warmer in winter and cooler in summer, and this is the main thing, not saving money - if saving money is your ultimate goal you are wasting your time bothering because you won't save anything.

[JupiterJon]

External insulation is a possibility but in my similar age property I intend to insulate the walls-without-windows internally and put double glazing in the walls with windows (sash box removal). This leaves the existing sash box and nice appearance and while not perfect shoudl be much better than oringally. The rooms are reasonably large in my case and it can be done room by room. One thing I know I will have to be careful with in ssealing between the cold wall and the now warmer wall to prevent condensation. There may be better ways.

2p Jon

[marvelus]

your full of shit

sorry

[Phil L]

Perhaps my earlier comments have confused you? - I'll try to keep the words short so that you can follow:

If he spends £500 on conventional CWI, and saves £60 per year, he will have broke even in less than 20 years, everything after that is profit. If on the other hand he chooses to have exterior insulation, it will cost him probably £3,500 and save him less than £60 per year - with me so far? - this means it will take him at least 58 years just to break even.

..sorry about having to use the word 'conventional', there's an explanation here:

[meow2222]

NT

[Phil L]

Obviously the 20 years should have read as 10 years, 500 divided by 60 is easy enough to work out.

[unopened]

You've forgotten depreciation, return-on-investment, opportunity costs, cost of capital, and all the other things accountants like to bamboozle us lesser mortals with.

Think of it this way. Assume, for the sake of argument, you can get 5% interest on money.

Invest 500 pounds. After 1 year, you have 525 pounds (25 pounds more). After 10 years you'd have about 814 pounds (314 pounds more), after 15 years about 1039 pounds (539 pounds more), and after 20 years you'd have about 1,326 pounds (826 pounds more).

Spend 500 pounds on insulation. After 1 year, you save 60 pounds, meaning you are only 440 pounds in the red. After 10 years you have saved 600 pounds, putting you 100 pounds in the black but you still have 214 pounds less than if you had invested the money instead. After

15 years you have saved 900 pounds, putting you 400 pounds in the black, but still 139 pounds less than if you had invested the money, and after 20 years, you have saved 1200 pounds, putting you 700 pounds in the black, but STILL less than if you had invested the money.

Now you can argue over 5% is reasonable, and whether your cost savings would improve as the price of fuel increases, and maybe you have had the benefit of a warmer house - (all things that accountants have fun with), but payback is not simple.

Cheers,

Sid

[meow2222]

Indeed. There are also the other 2 real life factors: with savings some people will just blow them on nothing, some will use them as a valuable backup fund, and for some the other option is to pay off some debt.

But still it doesnt tell us much unless he uses more realistic figures.

NT

[marvelus]

Cavity Wall Insulation reduces heat loss by upto 1/3

or prove otherwise!

So more like savings of £250 / year for a house that costs £500 to insulate. Even ignoring the grants and rapid increases in fuel costs it pays for itself in just over 2 years.

25mm Celotex has thermal resistance of 1.05 m2k/w compared to 4 1/2 inch brick thickness of 0.132. So an inch of celotex has same theremal resistance as a yard thickness of bricks. Far from "useless".

Sorry about my abusive tone earlier, I have a hard life:(

[Phil L]

I don't neeed to prove otherwise, I've installed CWI (both fibreglass and rockwool) in over 5,000 houses including my own (obviously!) and the savings are nothing like those claimed.

I'm afraid people are forgetting that moey used to be worth a lot more than it is now, IE if someone paid £200 for CWI 15 years ago, that £200 is like a grand today, so regardless of fuel prices, interest rates and everything else, that person is still in the red.

Solid insulation is not CWI, celotex can't be inserted into an existing cavity as the OP mentioned, nor can kingspan, polystyrene or anything else in rigid or semi rigid form, his only option (apart from exterior insulation) is to have it blown, and blown insulation is useless at less than 50mm thick.

on the blob?

[thomas.rynne]

Are you saying solid insulation can't be inserted into an existing cavaity because of access? I do have access at the moment as I have removed the chimney breast. I am about to brick it in. The wall is quite small so only about 2 feet of the interior wall remains - I could slide something into the remaining cavity. Also, now that I have removed most of the chimney breast I have better access and can see that the cavity is between 40 and 50mm.

Which would be the best option, rebuild the internal wall and then have it blown, or fit some insulation before building the wall. If the latter, can I just buy panels of insulation for that purpose? What are they called?

thanks Thomas

[The Natural Philosopher]

ALWAYS fit as you build if you can.

Not sure if rockwool cavity batts still meet regs, but they used to and are cheap.

Kingspan/celotex is better though.

Batts is what the soggy stuff is called.

Kingspan and celotex are sold in sheets and you must cut to fit.