So, moved in about half a year ago, boarding the loft right now. I plan on putting Kingspan in between the rafters, and I wonder... do I need ventilation, and if so which one. Here's a pic of the loft:
Close-up of the eaves:
And a pic from outside to see soffits:
Now to say this straight ahead, AT THE MOMENT we have no problem with condensation at all. All roofers attested that it's a pretty good breathable membrane. There's two Velux windows in there which we can obviously set to ventilate if needed, I have a decent dehumidifier and smart sensors if humidity should crop up. The plan is to turn the loft into mostly storage, maybe "hobby room" where I can put my tools and do some stuff on a rainy day, and that's probably about it. There's proper insulation on the floor (there were typical 1960s tiny 2x4 ceiling joists in there with a 100mm-ish or a bit more rock wool, I've added proper 6x2 joists mounted on wall plates/load-bearing walls, an inch above the ceiling joists, with 170mm rock wool which takes me up to a good 270mm according to regs). The rafters are 100mm so I'll put 50mm of Kingspan in between to leave 50mm air gap between insulation and membrane.
Do I need ventilation, and if so, which? I've contacted several roofers:
- One didn't even come over and just sent a quote for 260 quid to put in soffit vents (which I kind of suggested in my enquiry for the quote, and there's a chance they know the area as most contractors I contact do).
- One came over and basically said "don't bother". He said he wouldn't put in tile vents or anything like that as the air flow wouldn't go sideways, so not between all rafters anyways, it could just make everything more subjective to water ingress, and the most he'd suggest is soffit vents. But he said because my soffits aren't siliconed to the wall there's enough air gaps between/around them to allow, together with the roof's breathable membrane, for some air flow, and if there ever was any condensation it would drip to the bottom and I would see it on the soffits/wall and could put in soffit vents THEN. But for now, don't do anything.
- One came over and said soffit vents won't work because there's not enough space above the eaves for air flow, there would have to be eaves vents, and he suggested 3 tile vents on either side and a ridge vent across the top.
Other non-professional advisors (neighbours, friends, family) were kind of suggesting something similar to #2 - don't bother...
Not sure what to do, if I get more contractors over, if I just wait and see... thoughts?
Close-up of the eaves:
And a pic from outside to see soffits:
Now to say this straight ahead, AT THE MOMENT we have no problem with condensation at all. All roofers attested that it's a pretty good breathable membrane. There's two Velux windows in there which we can obviously set to ventilate if needed, I have a decent dehumidifier and smart sensors if humidity should crop up. The plan is to turn the loft into mostly storage, maybe "hobby room" where I can put my tools and do some stuff on a rainy day, and that's probably about it. There's proper insulation on the floor (there were typical 1960s tiny 2x4 ceiling joists in there with a 100mm-ish or a bit more rock wool, I've added proper 6x2 joists mounted on wall plates/load-bearing walls, an inch above the ceiling joists, with 170mm rock wool which takes me up to a good 270mm according to regs). The rafters are 100mm so I'll put 50mm of Kingspan in between to leave 50mm air gap between insulation and membrane.
Do I need ventilation, and if so, which? I've contacted several roofers:
- One didn't even come over and just sent a quote for 260 quid to put in soffit vents (which I kind of suggested in my enquiry for the quote, and there's a chance they know the area as most contractors I contact do).
- One came over and basically said "don't bother". He said he wouldn't put in tile vents or anything like that as the air flow wouldn't go sideways, so not between all rafters anyways, it could just make everything more subjective to water ingress, and the most he'd suggest is soffit vents. But he said because my soffits aren't siliconed to the wall there's enough air gaps between/around them to allow, together with the roof's breathable membrane, for some air flow, and if there ever was any condensation it would drip to the bottom and I would see it on the soffits/wall and could put in soffit vents THEN. But for now, don't do anything.
- One came over and said soffit vents won't work because there's not enough space above the eaves for air flow, there would have to be eaves vents, and he suggested 3 tile vents on either side and a ridge vent across the top.
Other non-professional advisors (neighbours, friends, family) were kind of suggesting something similar to #2 - don't bother...
Not sure what to do, if I get more contractors over, if I just wait and see... thoughts?
