Making loft conversion quiet and cool: soundcheck plasterboard, triple-glazed velux?

phil24_7

You will likely have PIR (foil backed foam insulation) in between the rafters (possibly with some over them) with plasterboard screwed through to the rafters.

The floor will likely need to be raised to allow the joists to be strengthened, just make sure the loft insulation that is there is kept or is replaced with PIR board (depending on available room). There will likely be no requirement for this as it is an internal floorspace but loose it and ALL heat from the house will rise to the loft. With insulation there it will slow this process, easing the load on any ventilation etc in the loft.

Insulating a solid wall would need a different approach depending on the situation.

phil24_7

What do the plans say about the conversion? What do the specs from the loft company say? What does the contract from the loft company say?

ic

I have a double glazed velux in my kitchen (60 model, not 50 which is a more basic double glazed unit). I originally wanted triple glazed (62 model) as all my windows are triple glazed, however there was a two week lead time on that, where as double glazed was available next day and I only realised this as the window was required by the builders.

When it rains it is very quiet, surprisingly so, and there wasn't much of a jump in thermal efficiency between the two - especially given the jump in price. I'd recommend that if the window is out of reach (granted unlikely in a loft) that you go for the Integra upgrade to add motorised automation to the window. I use it all the time, and the fact it auto-closes when it rains is a life saver!

zoothornrollo_2

Furts wrote: »

Have you scrutinised all the working drawings and the specification for the work? The fact that the loft company is dealing with that is worrying. This is your responsibility and any comeback is on you.

You have specific requirements, so to just say "the loft company is dealing with that" is, please forgive me for stating this, extremely foolish.

It's up to the loft company to submit building reg.s forms - that's what I'm paying them for.
Their job is to design and spec-out extensions that pass building reg.s - if I didn't think they and their architect were capable of that then I wouldn't have contracted them.
But they will inevitably spec things like windows and insulation to a fairly basic level that will just pass BRs. They are not going to give you triple-glazing and soundproofing if they don't have to.
I have taken advice from a chartered surveyor as to what sort of soundproofing an insulation is possible / desirable.
In the unlikely event he, I and the loft company are mistaken that the measures are permitted by BRs then the BRs man will tell us and we will have to change the spec. That's what BR inspectors are there for.

zoothornrollo_2

phil24_7 wrote: »

What do the plans say about the conversion? What do the specs from the loft company say? What does the contract from the loft company say?

It's just standard, double-glazed velux, standard width plasterboard etc etc.

"Foil backed, ridged insulation boards are to be measured and precisely cut between external rafters
and stud walls to meet the thermal values required.
Internal walls are to be constructed with 100mm x 50mm timber studs and filled with ISO wool insulation
for acoustics."

"The new dormer is to be clad with roof tiles to match existing roof coverings. Tiles/slates are to be
fixed to new tannilised roofing batten, twice nailed in accordance with manufactures guild lines.
Code 4 lead to be supplied and fixed to new roof junctions where required.
Flat roof to be constructed from peal-dec flat roofing insulation boards and covered with a three layer
high performance mineral roofing system."

"To supply and fix 2no standard white UPVC window units.
1no 1800mm x 900mm, 1no 450mm x 900mm
2no MKO4 Velux Windows"