I’m helping an to tighten up the insulation on a ’60s vintage house for an elderly lady. The roof is a 4/12 pitch, so there’s not much headroom in the attic! Her ceiling insulation is pathetic — currently a single layer of 4″ mineral wool batts. The attic has two gable vents (about 1 foot sq. each) and two roof turbines for ventilation. Total area of the ceiling is about 1300 sq. feet.
I’m suggesting we blow in a layer of cellulose but others say we have to add some soffit vents. The vents are going to be a real problem because there is so little room up there and I don’t see a way to keep the blow in from covering the holes.
Anyone else seen this situation? Thanks in advance!
Replies
I'm a believer in using either gable vents OR using a combination soffit/ridge vent.
If you leave it as is, just blow in more cells. Before you do, try pulling back the existing mineral wool and use canned foam to seal ant penetrations between the attic and the living space below.
If you install soffits, just use the baffles channel vents or use something you cobbble together to act as a dam to keep the cells from getting out and on top of the soffit vent.
If you do the full soffit-to-ridge, consider blocking the gable vents.
Some questions:
Where are you/she located?
What does the underside of the roof sheathing look like? Especially on the north side or shaded side. And down towards the soffits. A little dark "mildew"? A lot? Have boards had to have been replaced when reroofed in the past?
Slab, or crawlspace or basement? Sandy soils or clay? Wet under the house?
As a general rule, I'd say to stick with what you've got if there isn't much in the way of past moisture evidence.
What might be necessary will usually depend on the past performance of the house, not the "rules" in the code book or general rules designed to try to fit all situations.
Start with figuring out what what you actually have and how it has performed.
I don't know about yours, but my church isn't a hotel for the holy, it's a hospital for sinners
Sojourners: Christians for Justice and Peace
She lives in Mack, Colorado just East of the Utah border. Very dry climate there, so no signs of mildew at all. Temps range from -10F in the Winter to 105F on the Summer. Her house is over a vented crawlspace and that's where they ran the ducts and plumbing. We're just trying to cut her heating bill for the gas furnace. She has a swamp cooler for the Summer.The biggest problem I could see in the attic is getting near the eaves of the house because the roof line is so low. A midget would have a hard time even reaching the outer edges.
I don't have a clue as to how a house like that would perform.Check out the attic space, esp the roof sheathing to see how it has performed in the past and work from there.I don't know about yours, but my church isn't a hotel for the holy, it's a hospital for sinners
Sojourners: Christians for Justice and Peace
In my opinion, it's probably more important to seal penetrations than to insulate -- you should tend to the sealing first. Look around wires, pipes, and flues. Also check along the tops of wall -- often there are gaps between wall drywall and the top plate that allow air leakage. Use foam around wires and pipes, cut sheet metal flanges around metal flues. I've found that a thick "elastomeric" roof coating works well to seal the tops of walls.
If care is used, cellulose can be blown without blocking eave vents. It means leaving the depth a bit shallow in those areas, and it may mean that you have to take out the vent and clear it in a couple of cases where the cel gets out of control, but it'll work.
I would like, though, to hear someone suggest a good way to protect vents in a 4/12 attic. I've got the same situation and haven't figured out a good way yet.
dan.... a little labor intensive, but...
if you're using a standard poly-eggshell PropaVent , you let it extend into the soffit area... then you carve a ROUGH plug out of foam board and wedge it into the area between the top of the plate and the bottom of the Propavent..
you can seal it in place by a couple squirts of canned foam
most of the insul . contractors carry a bag of fiberglass unfaced.. and they wedge that in as a plug to perform the same function.... allowing a full depth of cellulose without filling the soffit
if it is new construction , you can do a lot of this dam building as you sheath, nailing plywood dams above the plate with a trough to allow the PropaVent thru..
again.. seal up any holes with a can or spray foamMike Smith Rhode Island : Design / Build / Repair / Restore
> if you're using a standard poly-eggshell PropaVent , you let it
> extend into the soffit area... then you carve a ROUGH plug out of
> foam board and wedge it into the area between the top of the plate
> and the bottom of the Propavent..> you can seal it in place by a couple squirts of canned foamMaybe it's just my slightly excessive girth, but I find it hard to even get close enough in a 4/12 roof to staple in the top end of the PropaVent. I suppose the plug (I had considered pieces of foam rubber for this) could be wedged in with a stick, but I don't know how one would get close enough to squirt the foam.
i don't know.. i've done some 4/12 truss roofs... not pleasant
the stick and FG plug is what usually happensMike Smith Rhode Island : Design / Build / Repair / Restore
Getting back to TOH bashing ;-), there is a letter this month from a homeowner (snappy planning, page 13) who says that everytime he opens a wall, he drills a 1/2" hole in the top and bottom plates and hangs a wire between them from a bent coathanger in attic to make future work a snap. He is in NJ. Sounds like he is a big fan of thermal chimneys from conditioned to unconditioned spaces. No comment on otherwise sealing those penetrations.
I've done just that using this jack solution, cept we blew in insulfill . It had two gable vents and I added 6 turtle vents and six 6x12"?? I think- sofit vents. I made up cardboard u-channel and fit it in the rafter bays and stapled the ends I could easily access. We blew it with not to much concern about it up against the roof at the eves. Big time improvement in the house and really helped out in the summer on the AC.
Was 1996 and was up there about a year ago and no sign of problems, we put new roof on this summer but not from heat problems, just old age.