Insulate attic in 1920s craftsman with converted attic
I just purchased a 1920s craftsman in Arkansas (cooling dominated) with a converted attic running through the middle of the house. The converted attic gets very hot in the summer (and I'm assuming cold in the winter). The attic space behind the front knee wall has no insulation and wood planks instead of sheetrock (thus no air seal). See the right side of this image so you can tell what I'm talking about:
There doesn't seem to be any insulation between the ceiling sheetrock and the roof deck.
The "attic space" towards the back of the house is much larger (under a hip roof). It also isn't covered in sheetrock (so no air seal). Here is a picture
On the accessible attic space, there is a couple of inches of blown in insulation and some knob and tube wiring (insulation isn't touching the K&T). I'm leery of adding more insulation to the attic floor because I don't want to cover the K&T. There are two turbine vents but no soffit, gable, or ridge vents in the attic.
My current plan is to use solid foam boards behind the knee walls to provide an air seal and some insulation for the walls. I'm not sure what to do to continue the air seal to the ceiling with the wood boards or insulate the ceiling.
Help!
Comments (12)
9 years agolast modified: 9 years agoRelated Discussions
Plaster in finished attic replaced with insulation and drywall
Comments (5)I do think from your description that the failure of the drywall ceiling is a result of lack of venting between the top of the insulation material and the underside of the roof. For starters, I would poke around and see if you have pre-formed (often pink, but possibly blue) foam pieces with ridges tucked up under the roof. These are installed between the rafters in cathedral ceilings (which is technically what you have from an insulation point of view, no matter how garrett-y your rooms feel). If not, then that's your problem (or problems) in a nut shell. You can research this on the Owens-Corning website which has lots of instructions about venting cathedral-style roofs. And you can look over these pieces at any Home Depot/Lowes. It will make sense when you see them. You may need to remove, install roof venting and replace the wall/ceiling surfaces. The plaster may be damaged more from aggressive removal of adjacent surfaces than from roof deflection, but one can't tell without studying it. And you may also need additional venting on the kneewalls now that the attic has been converted into living space which generates a good deal of moisture. You can cut down on this by installing proper vent fans for the kitchenette and bathroom areas, but you will still need under-roof ventilation, if not soffit vents, as well. It sounds as though the attic work was done by DIY amateurs. And that brings me to the most serious point that occurred to me: is it possible your attic has been converted into living space on the QT, and without benefit of building inspections, permits, (and unfortunately, increased property taxes) etc.? It may seem like a persnickety issue, but the chief risk in my opinion is that your attic living space - if done sub-rosa -might not have sufficient, legal, means of egress in an emergency. If you never have an emergency, it might not matter, but in the case of fire, inadequate escape routes can lead to the death of occupants and firefighters attempting a rescue. This is a very serious risk, and not one I'd care to undertake; it has the potential for devastating financial, legal, and even criminal consequences. While you noodle on that risk, you can research the catherdral ceiling vent issues on line. If you think structural compromise might be the reason for the plaster cracking, then an old-house friendly structural engineer (and many are not) would be the one you need. Consultations with roofers, insulation contractors and plasterers will not resolve the central issues and may lead to unnecessary, off-point work at this stage. Aside from permitting issues, however it doesn't sound that dire, though ripping and venting and replacing the wall and ceiling surfaces won't be any fun in the heat of the summer. HTH, Molly~...See MoreDIY attic insulation tips?
Comments (9)The cost is determined by the type of insulation used. The protective gear as well. If you use treated cellulose(the type installed by using a machine to blow it into the space), protective gear can be as simple as a nose/mouth type filter protective mask. Home improvement stores often let you use the machine for free when you buy insulation. Takes at least two people, one in the attic and one feeding the machine. If you use fiberglass batts, protective gear can be more involved. Eye/ear/face protection(depending on individual reaction to fiberglass), long pants/long sleeved shirts, or protective suits, for instance. I used the cellulose type for our current house. DIY was half the cost of a pro company---and yes, I got three estimates....See MoreAttic insulation replacement
Comments (19)Currently it is fiberglass batts, and it’s from 1963 and has been damaged. I haven’t personally been up there to look yet. My husband and the house inspector have been up there. Nothing urgent, but something we think should be done on our to do list. No we will not have living space up there, joists are not sufficient for that and there is very little headroom with the hip roof and square hour style anyway. The attic will never be “conditioned” as we do not have A/C and live in a climate in which is is not at all necessary to have A/C for comfort, and heat only runs at night for 3-4 months of the year. Our windows are open most of the day all year round. I am sure that the attic heats up a lot due to solar heat gain, though - so it does seem sensible that lining the roof with a radiant barrier to reduce solar heat gain into the attic would be more effective than insulating the floor of the attic as it is, to reduce heat gain into the house on those days that it does get uncomfortable. We have a new (one year old) energy-star roof. I understand what you are saying about the “envelope” and I assume that it would be necessary to ensure that insulation and any vapor barrier on the attic floor was removed in order to avoid trapped moisture? I know double layers of waterproofing can be risky in that way but if they are separate spaces maybe not an issue. what about the sound insulation issue - both external sound (road noise and neighbors) and room to room? I can only guess insulation on the attic floor does more for the latter....See MoreInsulate roof from inside rooms, not inside the attic
Comments (3)Spray foam the roof to create a a “hot roof” and making the attic assembly unvented. It’s a far more effective approach for warm climates. https://www.buildingscience.com/documents/digests/bsd-102-understanding-attic-ventilation...See MoreRelated Professionals
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9 years ago- 9 years agolast modified: 9 years ago
- 9 years ago
- 9 years ago
OP here.
My roof is in great shape so I won't be replacing it any time soon plus it has some interesting curves to it so adding rigid foam and sleepers over the roof deck might be more trouble than its worth. See pic:
I do have the gable vents and the giant vent over the porch so I think ventilation in the front part of the attic (the shorter knee wall in the original picture) is ok. I think what I've decided to do is to add soffit vents on the back of the house (where there are no intake vents). Then I'll install a foil radiant barrier on the bottom of the roof deck in all of the accessible attic areas. I will pull down the wood paneling stuff, add rigid foam between the studs in the knee wall as well as the roof rafters, and install sheetrock over it all. Its all 2x6 so I should be able to get 4 inches of foam (R20 or so) in there while still leaving a 2 inch gap for air flow under the roof. I found a guy on craigslist selling 4 inch closed cell foam at 75c per sqft.
I've also thought about being cheap and just using fiberglass batts (r16) with baffles on the roof deck instead of foam. That would cost r4 but save quite a bit of money. So long as I make sure I've got a good air seal with the sheetrock and plenty of ventilation, after that, its all down to r value right?
I've also essentially given up on the thought of spray foam on the roof deck. That would cost in the neighborhood of 5k plus the cost of ripping off and reinstalling the sheetrock.
- 9 years agolast modified: 9 years ago
- 9 years ago
Vith, Thank you for all of your help here.
I don't think I was clear about the radiant barrier. I am not planning on stapling it to the actual roof deck but rather the under side of the rafters like this (this is just pic I found online that shows what I mean):
Regarding where the vapor barrier should be located, I never know how to categorize Arkansas. We have several weeks out of the year that are above 100F and several weeks that are below 32F. It tends to be hot more than it is cold.
The foam that I found for 75c a sqft on craigslist is unfaced "CFC-free foamed-in-place polyisocyanurate foam 2.1 to 2.5pcf density". It is reject & miscut foam from a local walk in cooler manufacturer. The manufacturer claims that it is r8 per inch. (so 4 inch is r32 or so). If this foam is acceptable for residential attic insulation, it makes going from r13 to r32 only cost about an extra 50% more (75c for foam and 47c for fiberglass per sqft).
- 9 years agolast modified: 9 years ago
- 9 years ago
- 9 years ago
- 9 years ago
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