Insulating the Workshop Roof (by alaric)
I work from home, in my workshop at the end of the garden. I have my rocket mass heater to warm it in the winter, but while the radiant heat from the primary heat exchanger is comfortable, as soon as the fire burns down it's freezing again, because the room's air temperature doesn't really rise.
Also, in summer, I roast in here; the sun beats straight down on the dark felt roof above, and my ceiling is just four layers of felt and a couple of centimetres of plywood, so on sunny days the wood above me reaches 40-50 degrees Celcius and roasts me with infra-red radiation.
BUT NO MORE!
Because over this past summer, I've finished insulating the roof. I did this by getting inch-thick foil-backed foam boards and fixing them between the joists, with twenty centimetres of woolly insulation above that. Here's a few photos to illustrate what I mean, taken when I tested the method at the end of last year:
There's a gap of about five centimetres above the woolly stuff, to allow air to flow. A big danger of sealing a roof up with insulation is that warm, humid air from the room beneath will manage to sneak up, past the insulation, reach the cold area above, and promptly condense, making it nasty and dump up there - leading to the roof rotting. So I left an air gap, and made sure that every area of the roof was ventilated. Since the roof is punctuated by wooden beams, this meant putting an air vent at the top and bottom of each "bay". In the summer, the air rising out of the vents at the upper end of the roof was pretty hot, too, so convection of air along the underside of the hot roof also helps to get rid of heat in the summer.
Thankfully, this meant that I wasn't roasted during the summer; and now I've mainly finished running aluminium tape over all the edges, so my warm air doesn't seep up and dissappear, it's also keeping the heat much better in winter. I've been running the rocket mass heater in the mornings and the room temperature has risen and stayed up for most of the day, thanks to the residual heat from the secondary heat exchanger now being enough to replace heat lost to the outside.
Also, it seems the aluminium tape makes a good electrical contact with the aluminium backing on the foam board, so my entire ceiling is a big radio-frequency reflector, which might prove useful in keeping all the noise-leaking computers in my workshop separate from any antennas I put on the roof...
Alaric, Building Maintenance | alaric | 
Sun 8th Nov 2020 4:10 pm
Subscribe