Is 1 superquilt +1 insulation board warm enough for loft

[Lulunoclue]

Sorry if this has been addressed before but I can't find the info I need!
I'd asked about insulating rafters in attic and the best product between spray foam, superquilt, fibre wool or rigid board. The answer I got was to go for rigid insulation board in between each rafter.

I know that is best, but we don't want to do this (so please don't recommend) it's way too fiddly to cut it to the right widths and we certainly don't want to add hundreds of battens (either to provide a stop to maintain 50mm gap or to extend each and every rafter depth). It's a big attic and this would be too time consuming.

Daresay this won't be popular here but we are opting for superquilt recessing around /into each rafter cavity to a depth of 38mm (or whatever depth leaves 50mm of space behind) then we'll fix battens across outside rafters (or under to be more exact) and now for my query!! I've read that even 2 layers of foil quilt isn't warm enough so we'll just do 1 layer plus a different type of insulation.

But which insulation shall we add and what thickness?? If board (we'll get a width that doesn't need sawn along length LOL) would 50mm thick board and 1 superquilt be equivalent to the standard 270mm? I can't find any data for either on this. I beg of you not to go on about U or R ratings - the only thing I understand is 270mm of wool

Or if fibreglass /wool etc. what thickness and how do you get battens to be thick enough to take roll (without squishing)?

Sorry to be so long winded! There must be someone out there who has done this - if so, is loft room warm enough?

 

[kbdiy]

Are you insulating the loft to make it a useable room or do you just want to make the house warmer? The reason I ask is that you don't say why in your post and it occurs to me that you could be making work just for the sake of it.

 

[Lulunoclue]

hi kbdiy
Definitely not as a bedroom, but it will be used as a clean, bright storage area and sometime hobby room so we definitely do need it to be comfortably warm.

Also there will be a bigger, hatch (open to house below) to accommodate a space saving staircase (bigger ad less steep than ladder) so don't want cold air wafting down to us!

 

[tony1851]

What you are in effect asking is that someone sits down and takes their time to work out the heat loss of 270mm of glass wool between the rafters.

You then want them to take more time working out the thickness of board you would require, in conjunction with the foil, which would give you an equivalant rate of heat loss.

Seems like a big ask to me.

 

[Lulunoclue]

Err no, big, clever man!!! What I want is someone who has actually used superquilt in conjunction with something else to let me know if it worked and if so what product they used.

Don't think it's compulsory for you to chip in to every post, but if you've nothing better to do and it makes you happy, feel free!!

If anyone who does visit this site to offer useful advice (instead of abuse) I would appreciate hearing their views

 

[tony1851]

You miss the point, and here's why;

No-one puts 270mm glass wool between the rafters because of course it can't be done. Even if it could, the heat-loss characteristics of 270mm glass wool between sloping rafters will be completely different to the heat loss characteristics of 270mm glass wool between the ceiling joists.

That is why the U-values and R- values would have to be worked out to give you an equivalent thickness of whatever board you use.

That is why it would be a big ask.

As for asking anyone 'if it worked', that is subjective.

 

[Lulunoclue]

Sorry, when exactly did I say I expected to put 270mm in between rafters, where did that come from? Think I said between, around and below!!

I'm just asking if the equivalent warmth of 270 in wool can be achieved in other ways.

I've read advice on here before which I find confusing (we can't all be geniuses!) There's no point in getting technical with me, it won't help me 1 iota and it's help I want not someone showing off!!

And if someone has used superquilt and liked the results then that's good enough for me. I'd rather hear from someone who has done it rather than someone who talks about it.

 

[tony1851]

I'm just asking if the equivalent warmth of 270 in wool can be achieved in other ways.

You are insulating between the rafters, right?

You want someone to advise on the 'equivalent warmth' of 270mm of glass wool, right?

The point I was making is that the 'equivalent warmth' - as you call it - of 270mm glass wool on a ceiling (where it is usually applied) will not be the same as the 'equivalent warmth' of 270mm of glass wool on sloping rafters.
Someone would have to work out the reduced insulation value of the (hypothetical) quilt under the sloping roof.
Only when they've worked that out could they advise on an equivalent thickness of whatever board to go with your foil.

That's why it would involve some heat-loss calculations.

 

[Lulunoclue]

OK, I really wish you would stop repeating the same thing over and over - I think we all get that you're obsessed about dreadfully complicated heat loss calculations and the fact that I couldn't possibly put 270mm of loft roll between the rafters!! If I could have done that, I wouldn't be posting here re thinner combinations.

The attic is already floored but just has sawdust between joists which was perhaps insulation decades ago. I read somewhere that you don't need to insulate both rafters and joists ( though that could be wrong) so I'd prefer to do rafters and I just wanted the combination offering the highest possible value.

quote 'Someone would have to work out the reduced insulation value of the (hypothetical) quilt under the sloping roof'. unquote Would they? Someone must know the value of the quilt in relation to total required amount. Didn't realise I was asking for the impossible.

Anyway this convo between us (whilst amusing) is getting a tad tedious!! You don't bother me - if that's what you're trying to do. Just think trolling is a bit sad. What IS annoying is that you've obviously scared off more helpful posters who are terrified to add anything in fear contradicting you.

Don't think there's anything else to be said.

 

[leewallbank]

I wouldn't say Tony was the one who's scared off any other posters. It's more likely to be your attitude, you've come on here asking for help, he's trying to clarify what you're actually trying to gain and you're acting like a d#ck.

I've actually got 2 layers of superquilt between and above the rafters, it's early day's though as it was only fitted a few weeks ago and I've yet to insulate between the floor joists. Seems to have made a difference but haven't finished the attic yet so can't offer anything else.

 

[westridge177]

It strikes me that if tony had put the effort in he might have been able to help rather than just come up with negative vibes. I hate people who go around looking for reasons not to do something.

I wish I had the skills to answer, but as you've drawn a blank here try the technical help line from the manufacturer.

 

[geraldthehamster]

duplicate post, sorry

 

[geraldthehamster]

It strikes me that if tony had put the effort in he might have been able to help rather than just come up with negative vibes. I hate people who go around looking for reasons not to do something.

I wish I had the skills to answer, but as you've drawn a blank here try the technical help line from the manufacturer.

Tony's point (or one of them) was that this insulation isn't right for this application. Possibly if the poster had stayed to listen to what was being said to him, he might have gone on to learn something.

Cheers
Richard