Insulating my loft...

[microkid]

I have recently moved to a new house where some work has been carried out in the loft. This includes moving and reinforcing the roof supports, strengthening the floor joists, flooring and fitting a velux window. Infact pretty much a complete loft conversion except there is no staircase to go up so access is via a ladder (space in the rest of th ehouse is at a premium and adding the staircase would mean pretty much losing one of the upstairs rooms - of which there are only two).

I have building regulations for the work carried out 10 years ago so it has all been done properly.

I would like to use the loft as an occasional studio. However there is no insulation and the roofing felt is fully exposed.

What i the best way to insulate the space to keep it warm in winter and cool in summer?

What are the best materials to use?

I am thinking insulate between the roof rafters leaving a 50mm air gap between the underside of the roof and the insulation, then plasterboarding over the lot. Is this correct? What is the best way to ensure there is a 50mm air gap between the underside of the roof and the insulation? Do I have to use solid insulation sheeting like Celetex or kingspan? If so which one, how thick? Or can i do it with normal rolls of loft insulation? What is cheapest?

Is it possible to buy the sheet insulation cut to the correct width to fit between the rafters? or plasterboard sheets that are long and narrow so I can get them through the loft hatch.

All advice gratefully received!!!

 

[topgazza]

From a non expert point of view I can relate my loft conversion of a couple of years ago. They used Kingspan. It cuts very easy and yes, they allowed a gap between it and the roof...regulations for airflow. they also, regulations again, installed Kingspan OVER the roof joists...thus losing me about 3 inches of head clearance....then put plasterboard over that. Whether that applies to a room that is officially lived in or also applies to a casual used room I'm not sure.

 

[microkid]

yes I had heard that you can / should run a further set of insulation over the top of everything... but as I am not using it as a room for 'living' in I may not bother... I need to try and keep the cost down.

Do you know how thick the kingspan was?

Was it expensive?

How much air gap did they leave?

 

[MasterAbacus]

How big are the eaves? Maybe this part was not carried out as the wieght of the plasterboards would be too much for you roof timbers...???

How heavy do you think a dozen or so Plasterbaord sheets will be???

Tell us the dimensions...

If your not going to use it as a room, then why dont you just use that bubble Foil (Doublesided) stapled the the eaves?

 

[microkid]

I'm not at home at the moment but just look at my stick of inches i would say they are between 3 and 4 inches thick by 6 inches deep.

I would like to use it as a studio, so i need to think about sound proofing to a certain extent and also acoustic performance within the space itself. So any hard reflective surfaces are not really much use.

It looks from the number of nails sticking out of the eves that there was once plasterboard on there which can be confirmed by the broken bits left around the odd nail head. The were also 4 or 5 rolls of rock wool loft insulation in there when i moved in.

It i possible that someone pulled the board out to insulate then realised what a pain it would be with rock wool.....

 

[microkid]

sorry that was the dimension of the roof timber rafter.

I am unsure how big the eaves are, they dont look huge or small, kind of normal...

 

[MasterAbacus]

If you think the Eaves and structure can take the wieght of plaster board then id go for the Foil bubble stapled up, then plasterboard over that, its far easier than anything else and it will give you the min 50mm clearence too....as it will give you the Rafter width, which I asume would be minimum of 75mm anyway.

 

[topgazza]

..and lets be honest...who's going to know ? If it does the job and keeps it warm then jobs a goodun...


If you sell the house just don't describe it as a study or anything resembling a "converted" space that can be used to work/live/play in....a decent surveyor will ask for building regs/planning etc etc. Just tell potential buyers what you use it for...


Kingspan varies in thickess and the stuff they used in my loft is about 3-4 inches thick and its quite expensive I believe...

 

[Deluks]

You will never be able to get a loft room any more soundproofed than a normal room in the house. As mentioned the weight of plasterboard will limit you from beefing up the wall thickness, as will insulation requirements. Rockwool is definitely preferable over rigid for soundproofing qualities, but requires more depth-wise to get the same sort of insulation properties. Ideally you will want some rockwool on the inside of the room too, to cut down reverb from the plasterboard.

I'd be tempted to use rockwool between the rafters, leaving the required 50mm airgap between that and the felt. Batten out the inside, then affix 50mm foam insulation between this, followed by 15mm plasterboard on resilient bar. Still won't do many favours to people downstairs though.

 

[microkid]

if the roof structure is strong enough to withstand the weight of all those slates for the last 130 years surely adding a few sheets of plasterboard to the underisde spread accros the entire area isn't going to make much difference?

I have spoken to a retired architect about this and he almost laughed at the suggestion that the roof would be effected by this! so i am somewhat confused!

 

[MasterAbacus]

Well if you say its stood for 130 years then chances are its construction will be far more superior than any modern dayconstruction. How-ever is still be tempted to do the maths.... Work out how many sheets of Plasterboard you will be using, work out the total wieght, and asses from there....Mordern day roof trusses / structures are designed and built to a budget, and to take the tile wieght plus some small extra load....ie snow...Not that we get much of that here in the UK these days...