Which insulation - cold->warm deck flat roof

[jadzy]

Hi

After some advice on sensibly priced insulation for a warm deck flat roof conversion.

Background. My 58m2 flat roof needs redoing. Lots of cracking, holes through most of the layers, some lifting deck boards etc. Found out that under current building regs i need to improve my insulation. Threshold is 0.35U (iirc) and my current insulation gets 0.54U. So i now need to improve to 0.18U.

The current flat roof design is cold deck. There isn't enough space in the void for more insulation and an air gap. The joists are 125mm. So i'm looking into a warm deck conversion.

So now i'm trying to find an insulation that gets the required U value without costing the earth. Looking through celotex, kingspan, Recticel, ecotherm.

My roofer normally uses Celotex, and initially suggested td4126, but at a cost of 2600+vat. He has now found Recticel eurothane plylok 126mm at 2180+vat, so a little better. I've just found Ecotherm ecometer 120mm which is looking to cost at about 1100 for the insulation material, so plus fixings and labour to install. But again, cheaper.

Anyone got anything else they know of to offer?

Cheers

 

[datarebal]

£2600 for 58 mtr is resonable imo

 

[noseall]

£2600 for 58 mtr is resonable imo

Ditto.

 

[jadzy]

was worried you'd say that. might be the market rate but my wallet doesn't like it. seems i'm stuck with it?

 

[noseall]

was worried you'd say that. might be the market rate but my wallet doesn't like it. seems i'm stuck with it?

Unfortunately, we are all held ransom by a market that prices such things as Celotex and Kingspan at a similar level to gold and diamonds.

However, the rest of your job is bloody hard work and you should be glad to pay it.

 

[jadzy]

Happily leave this job to a professional. i take on too many jobs as DIY as it is. Most others i take on it doesn't matter so much if it takes a long time or it isn't right first time. But for a roof... i like my ceilings where they are

Currently being offered 2200+vat for refelting, plus all the adjustments to the facias etc of the flat roof and where it joins the pitch roof to take into account whatever height change results from the conversion to warm deck.

So the main job plus insulation is resulting in a very large bill.


The other option i might have is the 15 year payback for doing the insulation work. Not sure how to proceed with that. Gut feeling currently is it would cost as much to prove it wouldn't payback as it would to build it anyway! Assuming a token amount of additional insulation went in to improve what i have.

 

[jadzy]

Roof replacement underway..

Roofer has stripped old felt away. Lifted deck boards and is replacing the firings. The old ones only ran about a third of the way across the roof for some reason. He also found the roof joists aren't level, they are lower at the side that meets the pitch roof. So the previous firings and roof angle were making a very very shallow V shape. Anyway, new firings going in so the whole roof will now angle towards the gutter edge.

Toilet vent was also interesting... thought it vented straight into the void, but instead it was ducted to vent against the back of the facia boards. Whoever installed it hadn't bothered to bring it through the facia in any way. many years of moist air venting there had warped some of the surrounding wood a little. The detached drip of the old flat roof was in that spot funnily enough. Roofer putting that right too while he is on..

Old insulation is all removed, so not much on top to keep us warm tonight!

More work to continue tomorrow.

 

[noseall]

Keep us posted.

 

[jadzy]

went ok yesterday i think.

some rotting fascia board on the front of the house was noted and replaced. last bit of the old flat roof with stripped, new firings installed, deck boards replaced and a base felt layer installed. The man from building control was happy.

A amusing hangover from monday was sorted... hot bitumen had run through some gaps, pooled over the edge of the loft hatch and cooled to form a sort of hinge. so couldn't open the loft hatch at first.

Insulation day today... 126mm PIR/PUR to go on top.

 

[metalworks]

Hi

After some advice on sensibly priced insulation for a warm deck flat roof conversion.

Background. My 58m2 flat roof needs redoing. Lots of cracking, holes through most of the layers, some lifting deck boards etc. Found out that under current building regs i need to improve my insulation. Threshold is 0.35U (iirc) and my current insulation gets 0.54U. So i now need to improve to 0.18U.

The current flat roof design is cold deck. There isn't enough space in the void for more insulation and an air gap. The joists are 125mm. So i'm looking into a warm deck conversion.


Hi
What roofing material would you be using for your flat roof?

So now i'm trying to find an insulation that gets the required U value without costing the earth. Looking through celotex, kingspan, Recticel, ecotherm.

My roofer normally uses Celotex, and initially suggested td4126, but at a cost of 2600+vat. He has now found Recticel eurothane plylok 126mm at 2180+vat, so a little better. I've just found Ecotherm ecometer 120mm which is looking to cost at about 1100 for the insulation material, so plus fixings and labour to install. But again, cheaper.

Anyone got anything else they know of to offer?

Cheers

 

[jadzy]

It was done with 126mm recticel with the 6mm ply included. Can't call it a cheap option, but was the cheapest of the PIR/PUR i could find. The ecotherm turned out to be a tease... boards were about half the size of the recticel, so needed twice as many.

Make up of the roof is now, joists, firings (that go all the way across), 18mm ply (relaid on new firings) 1 base layer of felt (as vapour barrier and water proofer during further works) 126mm recticel (with 6mm ply top layer) 1 base felt, 1 high tensile mid layer felt, 1 high tensile top layer felt.

Remember your U value comes from all the materials in the roof, not just the insulation its self. Caused me some moments of frowning as you'll probably see typical U values quoted with a 200mm air gap/joist height. Mine were 125mm.

Man from building control was happy.. just waiting for my certificate or whatever i get now.

S

 

[Xenon]

There is a current wriggle in part L that says if you are repairing and not renewing, you do not have to insulate. Don't have it on this computer but opens up insulation options.

We pay about £20 M2 for 120mm PU. Didn't realise the domestic market was such a rip off.

 

[noseall]

We pay about £20 M2 for 120mm PU. Didn't realise the domestic market was such a rip off.

It is improving as more and more suppliers are springing up all the time.

 

[Xenon]

We pay about £20 M2 for 120mm PU. Didn't realise the domestic market was such a rip off.

It is improving as more and more suppliers are springing up all the time.

We buy a lot from Sheffield Insuation, always worth giving the local depot a call as they have regular clearouts. We've just binned about 200m2 of 90mm from our warehouse along with a lot of tapered insulation.

 

[jadzy]

If your current U value was above 0.53 iirc, then you have to improve as of about october last year. Or that was how i understood it now. I paid about £40 per m2, with the materials coming from jewsons. that was the best price i could find at the time. £20 would have put a big smile on my face. now it is just doing the oposite.