1990s roof insulation Vs modern??

[katie279]

Hi all,

Getting our roof replaced in a few months. We have an attic extension, so the insulation below the roof tiles is pretty key (rather than the usual piles of insulation you bung in the attic).

The extension was built in the early 1990s and it's a bit of an unknown what's under the roof tiles, but I'd be interested to know if there's any major difference between insulation put in in the 1990s and today.

I guess the two points would be

A) does insulation 'degrade' and reduce in effectiveness over 30 years

B) do modern celotex boards offer significantly better insulation than those in the 1990s

Can obviously ask the roofer's advice, but conscious that it's like asking a carpet fitter if I need to replace my underlay.....

 

[a1ex2001]

Building regs have changed massively since the 90’s so an extension built then will
Likely be significantly less well Insulated than the current regs require. I would be talking to your builder about how to get the absolute best out of the insulation and adding more where possible as this is likely a one off chance to do the work. Pretty shocked a 30 year old roof needs replacing mind!

On the underlay if you’ve had a carpet Down long enough for it to Need replacing then the underlay is almost certainly due replacing as well the key thing with underlay is to avoid paying the hideous price most carpet places change for the product!

 

[katie279]

Heh, roof is nearer sixty years - it was an attic extension that was done in the 1990s, not the whole house!

 

[jpaul]

https://www.ecomerchant.co.uk/news/a-brief-history-of-building-regulation-u-values-with-examples/

- looks like minimum ceiling&wall U value has reduced by 3x since 90's ... so should have 3x less watts lost per m2/K -
I'll have to do some measuring of the rock-wool thickness in the loft.

 

[bigfoot4616]

if there is any it will probably be rockwool, would be best to remove it and replace with as much celotex or similar as you can making sure you keep a 50mm air gap above the insulation. its very unlikely you'll be able to get enough in to meet current building regs so just go for as much as you can.

mine has 50mm celotex and 35mm insulated plasterboard(25mm insulation), the last job i did to regs a few years ago needed 125mm total insulation(celotex).

 

[theone8181]

This might be an interesting thread to follow as our house was built in the mid 90s and the insulation is about 150mm, is it worth doubling up on that or not?

 

[sja360]

This might be an interesting thread to follow as our house was built in the mid 90s and the insulation is about 150mm, is it worth doubling up on that or not?

Depends on what was fitted i suppose. Ie mineral wool, sheeps wool or something else.
I've got about 250mm on my loft as i read up to that is ideal, above that has diminishing returns on the cost.

I did also read some suggest leaving old insulation in and placing new on top to save on skip runs and waste, as if we threw out insulation every 15-20 years there would be even more waste at landfill.
Makes sense i suppose.

 

[Macky]

This might be an interesting thread to follow as our house was built in the mid 90s and the insulation is about 150mm, is it worth doubling up on that or not?

Yes. Building regs minimum loft insulation is now 270mm. Go and buy some top up rolls from B&Q and just lay on top of existing insulation if possible.

 

[Armageus]

I did also read some suggest leaving old insulation in and placing new on top to save on skip runs and waste, as if we threw out insulation every 15-20 years there would be even more waste at landfill.

Yep it's not easily recyclable and it's performance doesn't really degrade, so no real reason to remove.

Yes. Building regs minimum loft insulation is now 270mm. Go and buy some top up rolls from B&Q and just lay on top of existing insulation if possible.

Yep just go and buy appropriate thickness top up rolls (normally sold in either 100mm or 170mm), and then lay them over the top at 90 degree to the existing insulation

 

[theone8181]

Yes. Building regs minimum loft insulation is now 270mm. Go and buy some top up rolls from B&Q and just lay on top of existing insulation if possible.

Might go down that route as it will be cheaper than paying for the gas at the rate its going.

 

[jpaul]

Is upping the rockwool, practically, as effective, or is it less hydrophobic than PIR/cellotex so will get compromised, seems like it is about 2/3 of the efficiency of PIR.

 

[Armageus]

Is upping the rockwool, practically, as effective, or is it less hydrophobic than PIR/cellotex so will get compromised, seems like it is about 2/3 of the efficiency of PIR.

It will be cheaper and much easier to lay (i.e. badly fitted cellotex will be much worse than topping up his existing rockwool), than replacing the existing layer of rockwool with PIR/cellotex.

The main benefit of cellotex is that you only need ~130mm for similar effectiveness to 270mm of rockwool.

 

[Journey]

Heh, roof is nearer sixty years - it was an attic extension that was done in the 1990s, not the whole house!

I know you were looking at solar sooner rather than later, you know that you can get integrated solar so that the panels fit inline to your roof, if you are already getting the roof done it could save you lots of money (overall) and it looks much better.

Have a look here not recommending that company just to give you an idea of what is possible.

 

[katie279]

Yes, useful reminder - I'd originally looked at this and things like Tesla solar roof tiles which seem to have died a death (or at least underperformed and been very slow to roll out).

Had also looked at integrated panels like this, I believe they are less efficient for some reason.

It's an interesting thought - I'm not actually sure how much this would save as it might turn the roofing job into a building job (ie needing to coordinate two companies etc).

Might ask for a quote from roofer (ie how much would I save by not fitting X sq m of roof tiles).

I'd guess they'd also need to 'half do' the job - ie strip the whole current roof, re membrane etc then let the solar panel guys fit their bit, then go back and tile the rest, hence cost might actually increase in a way Vs 'get the roof done, then solar'.... Thoughts welcome!

 

[Journey]

A decent roofing company should be able to all of the work other than the final electrics and commissioning.

I'd ask your roofer who they work with if anyone, and if not it might be worth ringing/emailing a few others as its a much better solution.

The panels would only be less efficient if they are indeed less efficient, or got hotter ( not a UK issue normally) looking at most decent panels they are are all comparable to none integrated models even over the full 25+ year life span.

 

[bigfoot4616]

bloke next door to a job i was on last year fitted some integrated panels himself on his extension(he's a builder/roofer), just got someone to connect up. his roof is westmorland green slate so he "saved" a good chunk of money in needing less slate.

a decent roofer will be able to do just as good a job as anyone when it comes to the actual fitting of the panels.

 

[katie279]

Hmmm, roofer coming to quite this week, so will ask!! Great tips!

 

[mdaw]

Yes, useful reminder - I'd originally looked at this and things like Tesla solar roof tiles which seem to have died a death (or at least underperformed and been very slow to roll out).

Had also looked at integrated panels like this, I believe they are less efficient for some reason.

It's an interesting thought - I'm not actually sure how much this would save as it might turn the roofing job into a building job (ie needing to coordinate two companies etc).

Might ask for a quote from roofer (ie how much would I save by not fitting X sq m of roof tiles).

I'd guess they'd also need to 'half do' the job - ie strip the whole current roof, re membrane etc then let the solar panel guys fit their bit, then go back and tile the rest, hence cost might actually increase in a way Vs 'get the roof done, then solar'.... Thoughts welcome!

Solar panels can be less efficient when integrated due to a potential lack of air flow around them. If you have a warm loft rather than cold loft for example can make a difference. It is generally because when installed on the outside of a roof you will get air flow both on top and below. The hotter the panels get the less efficient they will be.

 

[katie279]

Ah that makes sense. Given we have an attic conversion, I'd imagine we'll veer towards the 'warm loft' option.

Will get some quotes and see what stacks up!

 

[Journey]

Ah that makes sense. Given we have an attic conversion, I'd imagine we'll veer towards the 'warm loft' option.

Will get some quotes and see what stacks up!

It's not such a big deal in the UK though, as we don't get long periods of very hot weather so the inefficiencies aren't even that big of a deal. If I'd needed to the roof done I'd have gone integrated regardless, especially for the savings and the neatness of the job.