Hi all
Last weekend (Sunday) we had a frost. Wnet in the loft that morning and found the tiling underfelt (early 70's house, so bitumen based and not breathable) wet with small drops of moisture on the underfelt across the north facing slope of the roof - the coldest surface. This is a detached house, standard brick build with cavity (foam insulation by previous owners years ago). The trusses were also damp where they touch the underfelt and PVC cables lying on top of the insulation also had condensation on them. Never seen this in the 12 years we have lived there and very worrying.
Had builder friend round who has suggested soffit vents to be added front and back to provide cross flow ventilation. The loft is not vented at all at present. How many soffit vents (the 70mm circular ones) and how close together?)
He's also suggesting we might want to up the insulation as at present its up to the top of the joists, but not over them also to current standards. However from reading many many thread over the past week I'm concerned that upping the insulation without improving the ventilation will cause a bigger condensation problem as the loft will get colder!
I thnk the soffit vents will help as I've spoken with www.roofconsult.co.uk, wjo also agreed good first step to try, folowed by tile vents high up to the ridge if this doesnt improve.
So what's changed recently:
1. Bathroom re-fit last summer (massive problems but another story!). Now has IP/fire rated downlighters, which although glass enclosed and sealed to ceiling with rubber washer, have open backs in the loft for heat to escape and have had to have the insulation pulled back from around them. Builder is proposing plaster board boxes around these with manufacurers recommended clearances before insulating over the top of them (I know this wont prevent water vapour rising, but pressumably it will stop the heat rising up).
2. Bathroom fan installed which goes out through the sofit. Seems to perform OK and religiously used - boys are showering more in there now. Wasnt leaving it over-running long, now understand I should let it over-run 20 mins and also now doing same with our en-suite shower. Very hard to check now if its properly taped up to the sofit extract connector, but may just have to take it apart from outside to check.
So bathroom(s) probably generating steam. We also leave windows open while showering, so with that and fans running I would hope we get rid of a lot of it?
We also leave bedroom windows open at night for fresh air unless its blowing a gale/pouring rain.
No drying clothes draped about house although it does go on clothes horse in small extension, that has a gas fire in - put on to help dry it. Suspect that is generating moisture so told wife to open a window and close the door when doing this.
We were drying some wet cloths in the airing cupboard ahead of noticing this and that probably also contributes. Pipe holes up from airing cupboard to be filled this weekend and habbit stopped.
No vapour membrane over bathroom ceilings (70's house!), probably not helping, so somehting to think about, but how would I install this with the recessed downlighters?
Cold and CH expansion tanks are insulated and doesnt appear to be any plumbing problems in the loft. The cold tank is actually raised on a platform, quite high on the trusses. It rests on a plywood base, but has no bottom insulation - wonder if I should do that (if so what with?). Also concerned increasing more ventilation at the soffits will make the loft colder (it feels cold now) and introduce a freezing threat to the told tank - am I going too far with that?
Sorry lost to consider - any thoughts gratefully appreciated.
Last weekend (Sunday) we had a frost. Wnet in the loft that morning and found the tiling underfelt (early 70's house, so bitumen based and not breathable) wet with small drops of moisture on the underfelt across the north facing slope of the roof - the coldest surface. This is a detached house, standard brick build with cavity (foam insulation by previous owners years ago). The trusses were also damp where they touch the underfelt and PVC cables lying on top of the insulation also had condensation on them. Never seen this in the 12 years we have lived there and very worrying.
Had builder friend round who has suggested soffit vents to be added front and back to provide cross flow ventilation. The loft is not vented at all at present. How many soffit vents (the 70mm circular ones) and how close together?)
He's also suggesting we might want to up the insulation as at present its up to the top of the joists, but not over them also to current standards. However from reading many many thread over the past week I'm concerned that upping the insulation without improving the ventilation will cause a bigger condensation problem as the loft will get colder!
I thnk the soffit vents will help as I've spoken with www.roofconsult.co.uk, wjo also agreed good first step to try, folowed by tile vents high up to the ridge if this doesnt improve.
So what's changed recently:
1. Bathroom re-fit last summer (massive problems but another story!). Now has IP/fire rated downlighters, which although glass enclosed and sealed to ceiling with rubber washer, have open backs in the loft for heat to escape and have had to have the insulation pulled back from around them. Builder is proposing plaster board boxes around these with manufacurers recommended clearances before insulating over the top of them (I know this wont prevent water vapour rising, but pressumably it will stop the heat rising up).
2. Bathroom fan installed which goes out through the sofit. Seems to perform OK and religiously used - boys are showering more in there now. Wasnt leaving it over-running long, now understand I should let it over-run 20 mins and also now doing same with our en-suite shower. Very hard to check now if its properly taped up to the sofit extract connector, but may just have to take it apart from outside to check.
So bathroom(s) probably generating steam. We also leave windows open while showering, so with that and fans running I would hope we get rid of a lot of it?
We also leave bedroom windows open at night for fresh air unless its blowing a gale/pouring rain.
No drying clothes draped about house although it does go on clothes horse in small extension, that has a gas fire in - put on to help dry it. Suspect that is generating moisture so told wife to open a window and close the door when doing this.
We were drying some wet cloths in the airing cupboard ahead of noticing this and that probably also contributes. Pipe holes up from airing cupboard to be filled this weekend and habbit stopped.
No vapour membrane over bathroom ceilings (70's house!), probably not helping, so somehting to think about, but how would I install this with the recessed downlighters?
Cold and CH expansion tanks are insulated and doesnt appear to be any plumbing problems in the loft. The cold tank is actually raised on a platform, quite high on the trusses. It rests on a plywood base, but has no bottom insulation - wonder if I should do that (if so what with?). Also concerned increasing more ventilation at the soffits will make the loft colder (it feels cold now) and introduce a freezing threat to the told tank - am I going too far with that?
Sorry lost to consider - any thoughts gratefully appreciated.
