Loft Insulation

stripling

https://forums.moneysavingexpert.com/discussion/comment/82143467#Comment_82143467

That's really outdated. 300-400 is the recommended minimum level now plus properly sealed and insulated hatches and good roof ventilation. I already had 270 and after a government survey was told to get it increased - it made a noticeable difference.

Thermal cameras are really useful for all this - lots of councils lend them out or you can hire one. They fit on your phone and are definitely worth the (minimal) effort. You'd be shocked at how/where heat is lost.

Just an FYI but Celotex and Kingspan are flammable and noxious - read the Grenfell report. It's a sorry state of affairs that they haven't been banned.

Rockwool thermal slabs are safer if you must use boards. But loft insulation on rolls is relatively cheap and easy to install.

ComicGeek

https://forums.moneysavingexpert.com/discussion/comment/82144360#Comment_82144360

If you have money to burn, by all means install 300-400mm - but for those people who are looking to make decisions based on real economic facts (rather than sales tactics from insulation companies) then there is very limited benefit in going above 200-250mm.

270mm is still the minimum level for new builds. Developers put more in the loft (400-450mm) for new builds as it allows them to save money in a different part of the house - cheaper to throw in another £120 of loft quilt than to make the cavity 50mm wider or buy better quality windows.

That doesn't automatically make it a good financial decision for existing home owners. Payback for that extra 100mm is about 10 years - I would choose to spend that money elsewhere first if working to a tight budget.

Section62

https://forums.moneysavingexpert.com/discussion/comment/82144360#Comment_82144360

Just an FYI but Celotex and Kingspan are flammable and noxious - read the Grenfell report. It's a sorry state of affairs that they haven't been banned.

The average house is stuffed with materials which are flammable and produce poisonous gases when heated/burned. Very unlikely they will all be banned. The roof structure of the typical home is timber - which is flammable - and when treated against rot/insect attack (as it should be) will likely produce some very nasty fumes when it burns.

If you have a fire in your home which causes the loft insulation to ignite then there's a far more serious problem than the combustibility and fumes produced by the loft insulation. It would be an unusual situation where the loft insulation is burning first, and in situations like that the flammability and combustion toxicity of the contents of the loft (if used for storage) would be an equal or greater issue. Banning the use of PIR insulation without banning the storage of flammable materials in voids (like lofts) would be illogical.

The issue with Grenfell related to whether the flammability of the materials used was sufficiently understood and reported, which resulted them being used in a tall building contrary (AIUI) to regulations. Being a tall building is a key issue due to various factors including the difficulty of firefighting, the greater time it takes to evacuate the building, and the necessity (in the case of Grenfell) of the 'stay put' strategy in case of fire. 'Stay put' works if the fire can be contained - if the building is constructed using materials and methods which don't contain the fire then the strategy fails.

If the lessons of Grenfell are going to be applied to one and two-storey dwellings - for example by banning PIR insulation - then there's some others with probably higher priority. For example banning open-plan living, providing a secondary means of escape (i.e. not relying on one staircase), and probably most important, strengthening criminal sanctions and enforcement against people (including DIYers) doing work contrary to building regs. My guess is the public appetite for this would be low.

missile

https://forums.moneysavingexpert.com/discussion/comment/82144796#Comment_82144796

That was my concern, I estimated 10+ years to pay back.

stripling

https://forums.moneysavingexpert.com/discussion/comment/82144796#Comment_82144796

No totally wrong. The extra levels advice was not from a company it was unrelated to any sales. It was completely independent and it turns out, accurate.

If you read my post this was backed by my own thermal camera images. I have the thermal camera and it was me that made the decision. Before and after images proved my point. Never mind that the heat loss is noticeably less.

The idea it costs 10 years 'payback' is absolute fairy land. Another top up layer of loft insulation is about £150-300 + insulation rolls IF you are paying for labour and this should include eaves plates at that cost. It's cheaper for a house than a bungalow. It's worth doing for comfort never mind cost. But why pay someone else?

It is an easy DIY job so would cost far less as there's no labour charges. There's plenty of good 'how to' videos on YouTube. This is why I recommend borrowing/hiring a thermal camera because it gives you facts not internet randoms.

stripling

https://forums.moneysavingexpert.com/discussion/comment/82146691#Comment_82146691

How do you come to that figure? What does it include?

stripling

@Section62 The average house is stuffed with materials which are flammable and produce poisonous gases when heated/burned. Very unlikely they will all be banned. The roof structure of the typical home is timber - which is flammable - and when treated against rot/insect attack (as it should be) will likely produce some very nasty fumes when it burns.

This is true look at the materials in furniture but we can still try to minimise things. There's various good loft insulation materials there's no need to use PIR. If you want to use boards you can use rock-wool boards although they are thicker.

The issue with Grenfell related to whether the flammability of the materials used was sufficiently understood and reported, which resulted them being used in a tall building contrary (AIUI) to regulations. Being a tall building is a key issue due to various factors including the difficulty of firefighting, the greater time it takes to evacuate the building, and the necessity (in the case of Grenfell) of the 'stay put' strategy in case of fire. 'Stay put' works if the fire can be contained - if the building is constructed using materials and methods which don't contain the fire then the strategy fails

This is also true but it wasn't about the flammability being 'understood' - it was deliberately obscured. They lied.

If the lessons of Grenfell are going to be applied to one and two-storey dwellings - for example by banning PIR insulation - then there's some others with probably higher priority. For example banning open-plan living, providing a secondary means of escape (i.e. not relying on one staircase), and probably most important, strengthening criminal sanctions and enforcement against people (including DIYers) doing work contrary to building regs. My guess is the public appetite for this would be low.

Absolutely agree with all of this. Sadly, our building standards are dire, particularly new builds. I have a big fascination with all this because of comparing building codes in other countries as a result of a project I'm working on looking at European decarbonisation. It's a 🐰hole.

missile

https://forums.moneysavingexpert.com/discussion/comment/82147714#Comment_82147714

I know how much I spend on gas for heating. I estimated what I might save. Then divided the quote = number of years.

QrizB

How do you come to that figure? What does it include?

I can't tell you how missile worked it out, but here's my attempt.

Consider a 3-bed semi with a total plan area of 50 square metres (ie. 100 sq.m split over 2 floors). Next we need some U-values. British Gypsum have a calculator here which suggests:

• 12.5mm plasterboard plus joists plus 200mm total insulation: U value 0.21 W/sq.m K
• 12.5mm plasterboard plus joists plus 300mm total insulation: U value 0.14 W/sq.m K
• 12.5mm plasterboard plus joists plus 400mm total insulation: U value 0.11 W/sq.m K

For 50 sq.m, at a temperature difference of 20K (21C indoors, 1C outdoors) the heat loss through the ceiling will be:

• 200mm insulation: 210 watts
• 300mm insulation: 140 watts
• 400mm insulation: 110 watts

If we consider a "winter" of 2000 hours (roughly 3 months), this means the total energy loss in kWh will be:

• 200mm insulation: 420 kWh
• 300mm insulation: 280 kWh
• 400mm insulation: 220 kWh

And then if we assume we're heating with mains gas at an effective price of 10p/kWh after boiler losses, the cost of the lost heat becomes:

• 200mm insulation: £42
• 300mm insulation: £28
• 400mm insulation: £22

So going from 200mm to 300mm will save £14 per year, going from 300mm to 400mm will save £6 per year.

What will it cost to add 100mm of insulation to 50 sq.m of loft? Well, Toolstation want £38.49 for a roll that covers 13.9 square meters. You'll need four rolls for the job, £154.

To save £154 will take 11 years at £14 per year, or 26 years at £6 per year.

There are some big simplifications in this; you might want to run your heating for longer than 2000 hours a year, and it might not be 1C outdoors for that entire time. But I think overall it's a reasonable estimate.

missile

https://forums.moneysavingexpert.com/discussion/comment/82147899#Comment_82147899

I am not physically able to DIY.

I know how much I spend on gas and during summer months where I use gas for water heating only. Thus I can calculate how much I spend on heating.

I am on a fixed tariff but do appreciate gas will likely increase. So I used a very optimistic scenario where insulation improvement reduced my heating cost by 40% and it would take me 10+ years to break even.