Loft insulated - Bring on the rain!
Monday, 04 January 2010 12:26
by Andrew Harmsworth
Property Type: Detached
Ownership Status: Freehold
What eco-improvements did you make to your property?
The house we bought early this summer had around 10 cm of loft insulation (at best). We topped this up to between 27 and 30 cm, whilst at the same time raising the level of the floorboards to retain storage.
What positive and negative experiences did you have?
Positive - the job looks brilliant and works: the heat losses through the roof are now much smaller. The major downside is CONDENSATION, which has not been mentioned on this website as far as I can see. We have two air bricks at the ends of our three gables. Sofit vents don't exist as the 'upstairs' of the house is enclosed by the slope of the roof. The six vents are clearly insufficient to clear water vapour which enters the loft and once temperatures drop below about 3 degrees outside condensation forms at rainforest levels on the underside of the black roofing felt. This has soaked into the rafters and drips/rains continuously onto the boarded deck, our belongings and onto the insulation itself! Essentially - the cost of buying the insulation (CERT subsidised) was negligible - about £50. The solution - fitting more vents or ripping it all out and installing a permanent vapour barrier - will be hundreds of pounds. If left unchecked, replacing the roof timbers in a couple of years when they've rotted through will be thousands. I'd like to see a good deal more warning about this sort of thing - the negative impact on the environment may be greater than the positive benefit of fuel savings.
What are the benefits to your home and lifestyle?
None that I can see, until we have solved the condensation crisis.
What advice would you give to others considering similar improvements?
Check that you have an excess of air vents and never block them. Do the installation slowly in the late autumn and monitor condensation levels on cold nights. Only complete the installation when you're satisfied that condensation is not going to be a problem - i.e. no drips when the temperature outside is around zero.
