That is a choice I'm considering in my residence to save the preceding house owners freshly put in roof shingles, nevertheless the depth on the rafters simply cannot accomodate sufficient insulation to fulfill code. I am thinking if I really should furr out the rafters to get the desired thickness of spray foam, or if setting up a few inches of polyiso foam to your underside of your rafters, once the spray foam, could work?
For sure, in some cases you might want to system in advance to be sure that your rafters are sized sufficiently to permit for insulation and venting. To learn more on suitable strategies to insulate lower-slope roofs, see this short article: Insulating Minimal-Slope Residential Roofs.
If you'd like to develop a conditioned attic, this text informs you what you have to know. To find out more on The subject, see Developing a Conditioned Attic.
It truly is undoubtedly not limited to an R 80 Passive Household roof. Just take out the parallel chord trusses and slim it up.
Martin, thanks. I just talked to your roofer and he rejected the thought of only putting the foam more than the spouse and children area cathedral ceiling. That Strange "jog" while in the roofline, owning it quickly bump up 4" or eight" wherever the spouse and children area commences, in the course of the back side on the roof, would defeat the idea of a steady slope for rain to return down when it hits the higher A part of that again roof. And so the four" or eight" height addition requires to continue throughout the complete 2nd Tale roof line.
I'm somewhat stumped on this 1 - I might want to vent this roof assembly, but I am unable to say whether or not there will certainly be a natural convective flow as there could well be with rafters sloping While using the roof pitch. My rafters are running amount However they sit on parallel curved top rated plates. I can use twelve" rafters and make 10" of batt get the job done, leaving plenty of ventilation Place. I'm able to drill the tops in the engineered joist flanges to allow air flow 'up-slope' (perpendicular into the rafters) and also inside the rafter bays, And that i can offer continual perimeter air flow (Cor-A-Vent strip) at my roof fascias (eave, ridge and gables).
one. It's usually a foul strategy to set up an HRV within an Discover More Here attic. HRVs must be available ample for the homeowners to routinely change the filter.
[Editor's Take note: Monthly bill Rose just sent me the subsequent remarks in an e-mail; he involved his permission to put up the comments.]
I believe you imply this: Your cathedral ceiling is presently uninsulated. When you find yourself indoors wanting up, you may see your rafters. Previously mentioned the rafters you may see a layer of boards. Is usually that proper?
I am with Martin on this just one, your depth is labor intense for very little if any gain in my view. The vent channels we describe can be achieved after the roof is on within the underside (dry facet). For people of us building in a chilly local climate that is a enormous edge, we spend as very little time as is required over the roof.
Looks like you might have the framing and roofing in position. Your choices are explained in the report higher than--you may increase venting by installing baffles below the sheathing to hold back again the insulation, or you may set up at least R-twenty of air impermeable insulation.
The code restrictions on the use of air-permeable insulation in between rafters had been produced to stop the roof sheathing from rotting. When fiberglass batts are mounted in unvented rafter bays, the batts allow moist indoor air to get to the cold roof sheathing.
Q. "I have already been applying rigid breadboard style expanded polystyrene within the rim joists and assumed the same could possibly be place underneath the sheathing amongst the rafter bays."
Unless of course a single makes use of Intense care with the warm aspect air barrier and this features being aware of that all fastener penetrations are sealed too you should presume some air flow. The set up referred to listed here with the ice and water protect under the shingles certainly manufactured an improved air barrier than whatever was on the warm side.