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I am in the process of refurbishing my attic flat. I have had to gain access into the sloping eves space so I might as well insulate while I am working in there- its an attic flat. On the vertical walls that are stud / lath and plaster what to do? Cut the celotex to go between the studs or build a solid layer behind the studs that will leave an air gap between the laths and the celotex?. There is zero insulation currently
Ta
pics?
You need a minimum of 50mm ventilation gap for roof timbers to avoid condensation. That assumes that the gap has some kind of air flow on each eave for cross flow. If not, you might want to install some vents to acheived this.
Same if these sloping walls are external.
Its quite tricky to take photos. the vertical part is about 1.5 m high and the studs around 40cm apart and of varying depth - with some diagonals. round the corner the vertical part is only 1m high but 9 m long. I hve a load of celotex that was surplus to requirements from a builder pal in varying thicknesses fromn 25mm to 150mm. I have already put a layer of celotex 50mm thick between the rafters on the sloping roof and the flat roof part is already externally insulated
[url= https://farm2.staticflickr.com/1742/42474208861_9b5bcac40b_o.jp g" target="_blank">https://farm2.staticflickr.com/1742/42474208861_9b5bcac40b_o.jp g"/> [/img][/url][url= https://flic.kr/p/27HiqvT ]IMG_1359[/url] by [url= https://www.flickr.com/photos/25846484@N04/ ]TandemJeremy[/url], on Flickr
science officer - the sloping part has a depth of around 150mm between the laths and the sarking boards and I have stuffed 50mm of celotex in there. Being a scottish roof it is fully boarded under the slates. Plenty of room for the air to circulate and I am not putting vents in - I had to do this in the other end of the building for planning and it caused massive drafts.
Its the vertical walls I wonder about - I have a triangular space to crawl around in and for air to circulate but am wondering whether a solid wall of celotex behind the studs or chunks cut to go between them
Ah, pic is useful.
Much less work to put the celotex across the back of the uprights - remember to seal the joint with aluminium tape to prevent moisture getting into the much colder now you've insulated space.
No downside to having a space between the laths and the insulation?
Its a bit odd as the offices below heat the whole attic via convection including that triangular space and it gets a lot of solar gain - (30c in there today) so its rarely at outside temps and only drops to around 8-10c even in winter and in the bit I have already done there is no evidence of condensation - too much airflow but obviously it gets colder at night and at weekends. the flat is noticeably colder on a sunday than a wednesday
I have already done one flat ( we own two in this attic ) and am aiming to make an insulated "cap" on the building
I'd keep working on the outer shell and add another layer between the roof rafters. That way you benefit from the heat lost by your downstair neighbours through that uninsualted floor and they too benefit from your insulation.
It sounds like your vents are too big. There are standards for inhabitied space but you don't need as much flow in that situation. I've got one 100mm vent with a mosquito netting for 70m2 and no trouble with condensation.
Have you bought the Celotex?
Because everyone is using this stuff now, its better because you don't have to cut it so exactly.
Its also cheaper. Comes in many thicknesses.
I got the celotex cheap - a mate who is a builder had over ordered. got about a thousand pounds worth for a few hundred. some of it cut into odd sizes tho.
I did wonder about that edukator but I would then have to draft proof the stud wall as well its gets drafty as the floor has shunk away from the skirting andI need to cut loads of holes in it for services so I thought two birds one stone. Given the eves space is drafty I don't see condensation is going to be an issue
I'd just fit the Celotex between the vertical studs. Job's a good'n.
A lot more work that way squirrel hence wondering if putting it behind the studs is any detriment and also behind the studs gets a more solid insulation barrier. Its a filty hot and awkward space to work in and I have 14m of wall to do
I don't think that would be detrimental, Â particularly as the roof void is ventilated. If you were concerned you could fix a vapour barrier to the face of the vertical studs first - polythene would do. I'm a building surveyor FWIW.
Thanks chaps
Ah the joys of old houses, eh? Coal must have been cheap as well as the maids running up and down stairs with buckets full of it.