An insulation question.
- Thread starter joe-90
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The governments idea of insulation is 12 inches or 30 cms of fiberglass.
The problem is, that fiberglass is rubbish as an insulation unless its in an airtight plastic bag, or air tight container. It also needs to be an almost air tight fit between the joists which in real life is impossible.
In your situation the best you can do is fill the spaces with a closed cell insulation, like Celotex, taking care to fill all cracks and holes with canned spray foam. You should be able to fill the spaces between the joists. This will give you a better result than fiberglass which is open cell. The cold air can blow through, warm air can rise through, water vapour can condense inside and turn into a wet mush. Wet fiberglass is 4000 times better than dry air at conducting heat from your home. Avoid at all costs!
The problem is, that fiberglass is rubbish as an insulation unless its in an airtight plastic bag, or air tight container. It also needs to be an almost air tight fit between the joists which in real life is impossible.
In your situation the best you can do is fill the spaces with a closed cell insulation, like Celotex, taking care to fill all cracks and holes with canned spray foam. You should be able to fill the spaces between the joists. This will give you a better result than fiberglass which is open cell. The cold air can blow through, warm air can rise through, water vapour can condense inside and turn into a wet mush. Wet fiberglass is 4000 times better than dry air at conducting heat from your home. Avoid at all costs!
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I think 170mm is standard for new builds, but 120mm is standard for home improvements, i may be wrong perhaps someone can correct if so.
It depends exactly which materials are compared but most loft rolls have a thermal conductivity of 0.040W/mK where Celotex has a thermal conductivity of 0.022W/mK - i.e. very nearly half. So 150mm of celotex is practically the same as 300mm of loft roll. Where you have to be careful is some manufacturers make rolls with slightly different thermal values. i.e. Knauf make a loft roll 44 - which is 0.044W/mK.
The thing to remember about quilt insulation is its ability to fill voids and prevent drafts.
To achieve similar results with rigid foam board insulation takes greater care, a few cans of foam and a roll of foil tape.
To achieve similar results with rigid foam board insulation takes greater care, a few cans of foam and a roll of foil tape.
We have been fitting Celotex all week and have been using the Soudal 'comfort grip' foam.
Effin brill stuff and very wieldy unlike the other cans.
http://www.youtube.com/watch?v=E0dQHwHHPWs
Well Joe, If you are in a good mood, you could always stick it up your ar*ehole, but as it would appear this is very seldom the case, we will have to give you a sensible answer.
The current L1B Regulations (existing dwellings) are .18W/m2K. You do not require 300mm fibreglass as previously stated as 270mm will comply. 100mm between and 170nn over the top.
270nn fibreglass with a K of .044 will give an R of 6.13m2K/W. plus external and internal resistance and plasterboard ceiling will give a total R value of 6.42m2K/W minus 10% for any possible cold bridging = 5.778m2K/W which will give a U value of .17W/m2K/
Celotex with a K value of .022W/mK.
125mm thick Celotex between the joists including additions for resistance plasterboard etc will give you an R value of 6.97m2K/W less in this instance 20% for possible cold bridging = 5.57m2K/W which equals .18W/m2K.
If you want to go Celotex route and joists are only 50X100, suggest you clunk a 50X63 on top. Your choice. Do me a favour and wait for a really hot sunny day before commencement.
Regards oldun
I'd split the difference, go with 100mm standard roll between the joists, for speed, then just plonk your king/celo/therm loosely on top, then screw your chipboard down with 150mm screws.
If your box of gimp suits and 1970's collection of 'Parade' are quite heavy, then counterbattening on top will add a little strength. You can do a run of insulation, add your 4x2 up snug against the side of the insulation, screw into place, repeat ad nauseam, or until you're sick of it.
If your box of gimp suits and 1970's collection of 'Parade' are quite heavy, then counterbattening on top will add a little strength. You can do a run of insulation, add your 4x2 up snug against the side of the insulation, screw into place, repeat ad nauseam, or until you're sick of it.
Timely as I have been contemplating much the same issue.
Presumably if the board is a good fit then no foam needed, otherwise foam in the gaps ?
Also, for those tight bits (between end joists/rafters and wall), is it OK to just foam in the hole rather than trying to get some thin slice of board in ?
And I guess, mark the position of all the walls etc, because it's going to be a right PITA adding things later (eg conduits for extra wall lights and so on)
Looks like a handy pack.
Presumably if the board is a good fit then no foam needed, otherwise foam in the gaps ?
Also, for those tight bits (between end joists/rafters and wall), is it OK to just foam in the hole rather than trying to get some thin slice of board in ?
And I guess, mark the position of all the walls etc, because it's going to be a right PITA adding things later (eg conduits for extra wall lights and so on)
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I'll have you know that I've got the largest collection of Health and Efficiency in the Midlands.
If ever you are passing then please feel free to come around and rummage in my boxers - err sorry - boxes.
Easy boy! (That's me that is).
If ever you are passing then please feel free to come around and rummage in my boxers - err sorry - boxes.
Easy boy! (That's me that is).
I'm not kidding when I say this stuff is a boon!
You start looking for holes to fill it is that handy. And there is the stopper to plug the end for re-use.
I have used their low mod silicone for ages and is also very good stuff. But this makes life a lot easier for those who don't have the benefit or the need for a foam gun and found those other cans clumsy.
You start looking for holes to fill it is that handy. And there is the stopper to plug the end for re-use.
I have used their low mod silicone for ages and is also very good stuff. But this makes life a lot easier for those who don't have the benefit or the need for a foam gun and found those other cans clumsy.
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