Insulating A Loft, At What Depth Does It Not Save Any Money?

[libspero]

If you're really keen try to find someone with a thermal imaging camera to see how much heat escapes everywhere else.

That might put into perspective any extra gain from more loft insulation?

[longtomsilver]

Our council is currently doing this for free, the priority is the vulnerable but anyone can have it done. I'm hoping that they will come and do the cavity wall for us. I might as well have a rebate.

Cavity wall insulation is a bad idea IMO bad for the building and bad for yor health. For that extra few degrees wear a jumper.

[Number79]

Cavity wall insulation is a bad idea IMO bad for the building and bad for yor health. For that extra few degrees wear a jumper.

+1

Look at the problems they are having in germany with the super efficient houses/flats that they have built to new regs. Mold and sick people everywhere. Houses need to breath. Insulating the loft is one thing but hermetically sealing the house to save a few quid is daft.

[snowflux]

Cavity wall insulation is a bad idea IMO bad for the building and bad for yor health. For that extra few degrees wear a jumper.

What's the problem with cavity wall insulation? My house has it, and I haven't noticed anything untoward.

[interestrateripoff]

+1

Look at the problems they are having in germany with the super efficient houses/flats that they have built to new regs. Mold and sick people everywhere. Houses need to breath. Insulating the loft is one thing but hermetically sealing the house to save a few quid is daft.

I think there is a bit of a difference between cavity wall insulation and making the house air tight.

If your going the air tight route you need very good ventilation, which ironically might cost you at least as much to run as the energy you save in stopping heat loss.

Agree totally about the need for houses to breathe, once I insulated the loft I knocked out a couple of bricks and put air bricks in to help the air circulate in the loft space.

[Dorkins]

What's the problem with cavity wall insulation? My house has it, and I haven't noticed anything untoward.

The insulation can wick water across the gap between the outer and inner layers of brick, especially if the outer wall is one that gets hit by driving rain (e.g. a west-facing wall in a rainy part of the country). Depends where you live though, if you live in the drier east you are less likely to have problems.

[Ash4781]

No idea on the physics. I just went to the energy trust site to get potential savings and calculate a present value ( go to a diy store for initial costs) or payback calculation. Though as other posters have said if you get it for free , great. Interesting if you go on the energy trust site some things take decades to pay back. Yes they save co2 but the financial decision is no!

[ntb]

A bit late in the day but I'll address the op. Basically, the inverse square law applies - doubling the insulation will halve the heat loss. Adding additional insulation will as you rightly surmise, reach a point where it is more cost effective to do something else. Speaking as a man with 39cm I would suggest you are sufficiently well endowed.

To do the calcs, you need to understand U values - watts per metre squared per degree centigrade of temperature difference.

As an example, a solid brick wall has a U value of approx 2.0 i.e. it will lose 2 watts of heat per square metre for each degree C temperature difference inside and out - so 40 watts for if it's freezing out and 20 degrees inside.

25mm of polystyrene insulation will halve this to U = 1.0 (20 watts)

50mm gives you U = 0.5 (10 watts)

100mm = 0.25 (5 watts)

200mm = 0.125 (2.5 watts)

400mm = 0.063 (1.25 watts)

Hope this helps.

[interestrateripoff]

A bit late in the day but I'll address the op. Basically, the inverse square law applies - doubling the insulation will halve the heat loss. Adding additional insulation will as you rightly surmise, reach a point where it is more cost effective to do something else. Speaking as a man with 39cm I would suggest you are sufficiently well endowed.

To do the calcs, you need to understand U values - watts per metre squared per degree centigrade of temperature difference.

As an example, a solid brick wall has a U value of approx 2.0 i.e. it will lose 2 watts of heat per square metre for each degree C temperature difference inside and out - so 40 watts for if it's freezing out and 20 degrees inside.

25mm of polystyrene insulation will halve this to U = 1.0 (20 watts)

50mm gives you U = 0.5 (10 watts)

100mm = 0.25 (5 watts)

200mm = 0.125 (2.5 watts)

400mm = 0.063 (1.25 watts)

Hope this helps.

Thank's for the info.

I'd only do it if there was a good offer on for insulation. I'd probably only need about 8 rolls.

Seems well worth having the cavity done on the wall where it can be. Hopefully I'll be able to knock down the temp on the boiler.

[ntb]

I think you may have miscalculated how much insulation you have in fact you probably don't have any at all so you might want to pay a visit here: http://www.npower.com/web/diyloftinsulation/index.htm

Cavity wall insulation is well worth doing but before you do, check thoroughly for damp at the base of your walls, especially if old. The reason is that mortar snots and debris can sometimes accumulate to the point at which they bridge the dpc and taking away the ventilation can then lead to more obvious problems with damp. Easily sorted by chopping out a brick or two to scrape the crap out and the insulation when added will prevent any recurrence.

[Gigantic Purple Slug]

You could probably pile on so much isulation that the roof would collapse under the strain (you may have to put it outside the tiles to cause this).

As the roof collapses, it would probably go through the first floor ceilings, then smash through to the ground floor, ruining you house contents and leaving you with a large pile of building rubble.

At this point it's safe to say you wouldn't be saving any money.