1 1/2 story cape cod, 1959, approx 2000 sq feet including basement.  "2nd" floor has shed-dormer almost the entire length of back of house.  Due to roof peak, upstairs rooms have ceiling height of about 6 1/2 feet.  2 bedrooms, 1 full bath, big walk-in storage closet.  From what I can see, the underside of the roof was insulated, the roof beams are 2x6.  The kneewalls are not insulated behind or anything.  No soffits, no ridge vents, no channels up the underside of the roof.

Everything I've read so far about Cape Cod style homes is that they are a beast to insulate and ventilate.  The attics behind the kneewalls can get quite hot and I can feel the heat radiating through the ceiling and kneewalls.

I had the shed dormer roof painted reflective white and that's helped a bit, but I'm sure the small amount of insulation on the roof, probably 6 inches total, and the lack of soffitt/ventilation is a problem. 

Are their any new ideas for these roofs nowadays?  Can one build a "cold roof" over the original roof with an air gap for ventilation? Even just like a floating metal roof or something to "shadow" the original roof and take care of some direct heating?

Sorry if this is posted to the wrong forum.  I'm looking to make improvements.

I think a cold roof would be a good solution.
If your in a cold climate it's that or reframe the roof with deeper members.

In an environment of future energy prices likely getting higher and higher you would be better served by taming the 1 1/2 story beast with a for sale sign.

Sorry, SE Pennsylvania. If we reframed the roof, I'd probably get the whole thing raised a couple feet, more head room, more insulation. Looking for a less costly alternative to reducing some of the heat in the summer.

Just bought the house...SIGH.

Would I ask a contractor for a "cold roof"? I'm thinking one could lay "furring strips" or something similar vertically up the front of the house, nailing them directly through the existing shingles, then have some sort of standing-seam metal roof applied to the furring strips. This "floating" roof would be perhaps an inch or two above the existing roof. The lower part, where the soffit vents are typically found would just be open, and the bottom edge of the roof would lead directly into the gutters anyway.
The top of the metal roof would be either overhung to the flat shed dormer a foot or two, to minimize rain getting between the two roofs, or sealed to the peak of the house with a proper weatherproof vent across the top (ridge vent, I guess).

This would "shadow" the whole original roof and provide an air gap for ventilation, keeping the original roof cooler, thus the attic spaces, thus the upstairs.

Would additional insulation be needed under the metal roof at all?
Would color of roof make that much difference? Aesthetically, that darkish red metal roof would be most appealing on my house.
Would the sides have to be sealed in order to force the air into the bottom and out the top, or wouldn't it matter if air came in the sides, too?

Would this be a $5000 project, or a $15,000 project?

Would it be worth it??

Stuart
It is not going to be an inexpensive project, but your basic problem is lack of insulation, so spending money on a metal roof or any other scheme which does not involve adding insulation will be money wasted.
Ventilating your existing roof would allow the heat you are buying (from your oil dealer) to disapate faster into the atmosphere. Better to try to keep in inside your house. I'd suggest you consider adding insulation from the outside - that would be far less expensive than reframing the roof. Start by Stripping the shingles and sheathing from the roof, block off the soffit and ridge roof vents, then fill the 2x6 rafter cavity with cellulose insulation or fiberglass batts. (Depending on the existing insulation, your contractor may be able to blow in new insualtion without removing the sheathing, or by only removing some of the boards.) Then add a layer of nailbase insulation - foam and plywood - available from commercial roofing supply companies above the existing sheathing and reshingle. A discussion of this method can be found on the General Forum - Residential - "Insulating Cathdral Ceilings from Above".
Yes the color of the roof makes a difference - lighter roofs absorb less heat and are cooler.
Bob

The house already has no soffits, no ridge vents, and fiberglass batts in the 2x6 cavities. I'd read somewhere on line that with a Cape with a finished upstairs, you can either insulate it, or ventilate it, but not both. Sounds like leaning towards insulate rather than ventilate. I'm just trying to get rid of excess summer heat that clearly stores up in the attic. For example, the master bedroom with an a/c duct maintains a nice 78 during the day. But open the clothes closet, built into the very end of the house and separated from the master bedroom by drywall and a hollow-core door, the temperature in the closet is 97. I've measured it.

Bob, you're thinking, if I read it right, that I should keep the house as-is, but on the outside of the house, remove the shingles, lay extra insulation, new plywood, and reshingle...basically try to block the heat from coming in, and then try to further completely seal the inside of the house up. The attics become "conditioned" space.

I think the worst part of the house is the big walk-in closet at the top of the stairs that is built under the front roof slope. You can see the 2x6 rafters and insulation bats. You can feel the heat in that space in the summer, and the RETURN vent for the upstairs a/c is *in that closet*, and the closet doors are louvered that lead to the upstairs hallway. Why do I think my a/c is pulling superheated air into the return??

That does sound like a pretty clear problem, having the return in that closet. Insulation should keep the heat in in the winter and out in the summer, so it will benefit you all year, whereas ventilating will help only at certain times. I dont know if you've been there in the winter but if not you may find that the house is also very hard to heat.

I was going to suggest you fasten foam to the inside of the rafters in the closet, but you also have the concern of creating cavities where moisture can condense and cause mold or rot, so there are numerous concerns. Sounds like it would be helpful to get someone to your house - look online for professionals in your area affiliated with NESEA or REPA; people knowledgeable about current building science who can help you devise insulation techniques that will work in your situation.

Posted By stuart.wyss on 24 Aug 2010 07:58 AM
The house already has no soffits, no ridge vents, and fiberglass batts in the 2x6 cavities. I'd read somewhere on line that with a Cape with a finished upstairs, you can either insulate it, or ventilate it, but not both. Sounds like leaning towards insulate rather than ventilate. I'm just trying to get rid of excess summer heat that clearly stores up in the attic. For example, the master bedroom with an a/c duct maintains a nice 78 during the day. But open the clothes closet, built into the very end of the house and separated from the master bedroom by drywall and a hollow-core door, the temperature in the closet is 97. I've measured it.

Bob, you're thinking, if I read it right, that I should keep the house as-is, but on the outside of the house, remove the shingles, lay extra insulation, new plywood, and reshingle...basically try to block the heat from coming in, and then try to further completely seal the inside of the house up. The attics become "conditioned" space.

I think the worst part of the house is the big walk-in closet at the top of the stairs that is built under the front roof slope. You can see the 2x6 rafters and insulation bats. You can feel the heat in that space in the summer, and the RETURN vent for the upstairs a/c is *in that closet*, and the closet doors are louvered that lead to the upstairs hallway. Why do I think my a/c is pulling superheated air into the return??

Ventilating the roof will not make a change in the cooling aspects that you'd even notice- you might be able to measure it with instrumentation, but if it increases the over all infiltration factors of the house (as likely not) it'll INCREASE rather than decrease your heating & cooling costs.  The primary benefit to vented roofs is that they're self-purging of humidity- the effect on roof deck temperature is negligible.

You say you've already mopped on some white goop to the exterior (hopefully it was a CRRC rated cool-roof material with an aged SRI>>75).  If you're going to insulate, insulate with something with lower infra-red transmission and air-convection characteristics than the lowly fiberglass batt, which sucks on both counts.  In a ventilated roof with R13 or R19 batts under a 130F roof deck a significant amount of radiated heat from that roof will penetrate at least a couple of inches into the batt, being absorbed by the fibers themselves.  The upper portion of the batt will convection-cool to near the ventilation air ambient, making the hottest part of the batt ~1-2 inches from the outer surface, since it's insulated from the the ventilation air.  This means your insulating against something close to the full roof deck temperature, with 1-2" LESS thickness to the batt. In an R13 batt you're looking at about R7 performance, in an R19 batt you're looking at ~R13.  Something close to the full-R can be restored by putting a radiant barrier between the roof deck and batt with at least 3/4" of clearance on both the roof deck & batt side of the RB, but that leaves you no room for the batt in a 2x6" rafter bay.  But there are solutions- use an insulation that is more opaque to IR radiation.

Depending on your climate the options will vary, but closed-cell spray foam will work in any climate, and a full cavity fill on a 2x6 rafters would render something like R30+, with no convection or IR radiation loss.  Some other options (and the relative moisture risks depending on climate zone) can be found here.  Dense-packed cellulose can be used in many locations, which would also add some thermal mass to the equation, reducing peak loads.  (Wet-sprayed cellulose can be substituted for spray fiberglass in that analysis as well, and would provide the code-required thermal barrier against ignition in place of gypsum where spray foam is used.)

If you're NOT going to insulate, radiant barrier applied to the rafters or radiant-barrier paint sprayed onto the interior of the roof deck will do some good.

When it's time to re-roof (probably not soon), adding a few inches of panelized rigid foam insulation above the roof deck can boost your R and give you an excellent thermal break over the conductive heat bridging of the rafters.  There are panelized goods that come with an OSB nail-base for applying standard roofing materials (Hunter Panels, Atlas, JM, etc all make this type of product, usually sold into commercial applications.) This is an appropriate treatment for an un-vented roof in any climate zone.  The more R-value you can put exterior to the structural wood the better protected it is from humidity issues. (This goes for walls too.)  A 4" thick panel of nail-base iso gives you another R20.  A 4" panel of nail-base EPS delivers ~R15.  The R-value across a 2x6 rafter is only ~R5, thus with an R30 cavity fill of 2lb foam that R5 will dominate the heat transfer through the roof, but with as little as R15 above that rafter you're now looking at a R20 as the minimum R anywhere on the roof- it counts.

 Details of "best practices" will vary with climate, but there are workable air-tight unvented attic designs for any climate, and that's likely where you're going to have to go with this to truly tame the beast.  Got a zip code?

18976 Warrington, Pennsylavnia

And the white goop stuff must have been someone else....I've never scraped anything like that off the roof. I had the shed dormer roof painted with reflective paint, but that's all.

So, maybe closed cell spray foam *in place of* the fiberglass to help block the heat? That I'm sure I could both investigate and afford.

If the reflective paint on the shed dormer roof is shiny-metallic looking it's likely to be a low-E aluminum paint which will run hotter than a high-E white.

Replacing the fiberglass entirely with closed cell polyurethane foam will work, but on the expensive side (it'll run about $6 per square foot to do an R30 fill.) An inch or two of closed cell foam, filling the rest of the rafter-bay with wet-spray cellulose or high-density wet-sprayed fiberglass works in your climate zone. A 2" foam layer delivers ~R12, and the remaining 3.5" of cellulose or fiberglass would put you in the R25ish range total. Wet-sprayed goods at 3"+ make the foam fire-code legal even without interior gypsum, which makes it even cheaper/easier when insulating the roof deck behind the knee walls. If you went with only 1" of foam you'd be looking at ~ R22-R23 after you fill the rest with sprayed fiber, and the total cost would be about half that of a full-closed cell job. If PA &/or the local utilities are generous with subsidies on retrofits it takes a bit of the wallet-sting out of an all closed-cell foam job, and with 2x6" rafters it would be the best overall option. It'll have more than 2x the performance of your batts, both summer & winter.

A somewhat cheaper closed cell option would be medium-density Icynene (tm), which would give you about R25 for ~$4/square foot. (5/6 of the R value at 2/3 of the price compared to most 2lb SPF.) Don't get it mixed up with their low density open cell stuff though- it's much cheaper & lower-R, and long-term could create roof deck rot issues in your climate (unless you add R from above the roof deck.)

Whenever re-roofing or re-siding a house, adding exterior insulation is usually a good idea for more reasons than mere R-value alone. By keeping the structural wood warmer in winter it stays drier, making it less susceptible to rot/ants/termites, etc. And by thermally-breaking the structural timbers you're less susceptible to ice damming on the roof, or heat/cold striping on the inteiror from those thermal-shorts. Without exterior insulation localized spots in the walls/ceilings where the framing is dense will always be hot in summer, cold in winter- often noticeably so when sitting near it. Even when it's not cost-effective from a mere NPV analysis on fuel savings, the long term structural protection & comfort factors still count for something.

Yikes! I just went into the attics behind the kneewalls and pulled a little at the insulation. Looks like it was probably installed in 1991, when the upstairs of the house was finished. The paper backing is very very dry and the fiberglass extremely dirty and "compressed". It looks like it "flattened "down from the plywood "under roof" and now the insulation is only about 1" thick of compressed dirty fiberglass. This is most likely throughout the entire roof, including behind all the finished ceilings. I can look right down the air "gap" between the fiberglass and the roof decking to the outside of the house...maybe soffit, but I know I don't have any kind of venting at the top.
Oh boy, what a mess. Can post pictures if desired. Stressed about the best approach now.

That inch of dirty compressed fiberglass is probably giving you a healthy R2.5- R3, so, what's the problem? :-)

It's dirty because it's been filtering the vented-roof-deck air. And without an air-barrier on that side it's rated R was never achieved even on day 1.

Short of stripping the roof deck over the finished ceiling to foam it from above, or stripping the interior and foaming it from below, if the rafters are 16" o.c. with 1/2" gypsun on the interior or 24" o.c. and least 5/8" gypsum you can probably just dense-pack the cathedralized ceiling portions. With that much air space it'll be easy to snake a dense-packing tube in there- no need to pull the dead batts. The end result would be ~R20.

If you CAN pull the dead-batts and the roofing nails aren't poking through the deck too far, there are installers capable of squirting half-pound foam to the far end of rafter bays and wall cavites, but the first place it sticks and expands to block line-of sight before it's been filled behind will cause a void in the insulation layer- dense-packing cellulose would be a safer bet. If the nails are all popping on the ceiling gypsum odds are you won't be able to dense pack it though. (A competent installer would assess that before and give you thumbs-up or down.)

Taking the long view it's probably worth demoing the ceilings and putting in closed cell foam if you can't dense pack it. But that's a bit messy while living there.

It sure explains the comfort-level issues in the attic rooms in big way though. They might have been R7-R8 (2.5" thick) econobatts on day 1 and only sagged an inch or so over the past 50 years. I doubt R11 batts would have sunk that far, but maybe.

Exactly. I just checked all 3 attic spaces behind the kneewalls, and all the insulation is much the same.

Probably with some sort of extension tool, all the old batts could be pulled out....they extend up the diagonal slope of the roof about 4 feet.

The nails are definitely sticking down through the plywood roof deck. The spray foam/cellulose would only need to get a nozzle up about 4 feet up the diagonal slope...that doesn't seem too difficult.

One guy came by today to look...he's in the "ventilation" school. He wanted to pull all the insulation away, leave it bare, and insulate the floor behind the kneewalls, the kneewalls themselves, and then try to shove baffles up the 4 foot slope along with new batts. But with no ridge vent on the house, I can't honestly see how that would help.

I'm hoping to talk to a spray-foam guy soon, too. My thought it just seal everything up as tight as possible and in the future, redeck the roof extra foam/plywood or that new roofing system with built-in baffles/ventilation.

Posted By stuart.wyss on 10 Sep 2010 11:08 AM
Exactly. I just checked all 3 attic spaces behind the kneewalls, and all the insulation is much the same.

Probably with some sort of extension tool, all the old batts could be pulled out....they extend up the diagonal slope of the roof about 4 feet.

The nails are definitely sticking down through the plywood roof deck. The spray foam/cellulose would only need to get a nozzle up about 4 feet up the diagonal slope...that doesn't seem too difficult.

One guy came by today to look...he's in the "ventilation" school. He wanted to pull all the insulation away, leave it bare, and insulate the floor behind the kneewalls, the kneewalls themselves, and then try to shove baffles up the 4 foot slope along with new batts. But with no ridge vent on the house, I can't honestly see how that would help.

I'm hoping to talk to a spray-foam guy soon, too. My thought it just seal everything up as tight as possible and in the future, redeck the roof extra foam/plywood or that new roofing system with built-in baffles/ventilation.

Trying to make the floor behind the knee walls and the knee walls themselves air tight is a labor intensive & losing proposition- I know, I've starred in that movie as the fallen victim!

Every joist bay below the kneewall has to be individually air-sealed to the ceiling below and kneewall to keep soffit-ventilaiton air from penetrating deep underneath the finished room floor.  I gave up when I figured out that the cross sectional area of the spaces between the hardwood flooring & shiplap subfloor was many times greater than all of the electrical & plumbing penetrations combined, despite the rosin-paper slip surface between them.   The plaster & lath ceiling below made air-sealing the joist bays nearly impossible as well.  It didn't take high math to figure out that foam-sealing all of that stuff would take more time & material than foaming the roof deck, with a much more assured result. Making the roof deck the pressure boundary of the house with foam or dense-packed cellulose is more realistic than tightening up the kneewall/attic floor L.

If you're only looking at 4' of cathedralized ceiling you might even do that section with a slow-rise foam pour rather than trying to use a spray-gun past 1001 nail points(which may be doable if you can pull the old batts.)   Ask the foam installers which would work the best after they've given it a good look.  Snaking a dense-packing hose in there would be dead easy, with or without batts in place.

Bumping this thread...

My new idea is this:
Soon - demo the flat part of the ceiling (shed dormer), remove batts, spray foam everything, sealing it up tight (no soffit openings, nothing) to make the entire attic behind the knee walls and above the shed dormer ceiling into conditioned space. Then (with approval of architect or structrual engineer) remove multiple ceiling joists and put drywall on the underside of the roof rafters. I'm hoping that even though the ceiling is being "raised" into the attic for more headroom, that 6 inches of foam under the roof, plus the new roof decking/venting (below) will improve things. I'm also thinking of having the siding on the top of the house removed and replaced with insulated siding. The other day, with an infrared thermometer, some of the upstairs walls (interior) had a temp reading of 50, even though the heat was on to 68.

In the next year or 3, redo the roof from the exterior by removing the shingles, adding foam board, new plywood, and shingles, and/or using that "vented" decking that adds soffit-to-ridge venting between the original plywood and this new decking.

Stuart
The roof work sounds like a good plan. I'd leave the siding for now; I assume you are talking about "insulated" vinyl siding? I don't have any test results, but I'd be very surprised if it is worth the money. They typically have a very thin layer of foam - 1/2" or less, so that would add only R-2 and do nothing about air leakage/infiltration. 50o interior walls indicates that there is cold exterior air getting into those walls! You need to get an energy auditor there to find the source of the air infiltration, but you could wait until the roof is stripped of insulation and the vent holes are plugged.

I spent much of yesterday clambering around in  the attic spaces behind the kneewalls.  Fortunately, there are little access panels in the closets at the ends of the roof. 

I was saddened by why I saw.  There are literally holes big enough to put my leg through that lead directly to the soffit space along the front of the house.  These holes lead directly into the space behind the kneewalls (uninsulated kneewalls - roof rafters are insulated, but still lots of big holes into the attic).  Space behind kneewalls is directly connected to all the joist cavities that run the entire width of the house, and also found several areas in the attach where I can see the tops of the exterior cinderblock walls of the first floor, and can look right down the inside of the cinderblock to the bottom of the wall.

Cold air can easily get from directly outside, into the kneewall attics, into the rooms, into the walls, into the floor joist spaces.

ANd I wonder why it's cold...and the traffic is so clearly heard...like it's just an open window.

Bingo! That explains the 50o walls. You read the term "airsealing" a lot nowdays; this is exactly the next stage for your project. Closing up these areas will go a long ways towards taming your energy hog. Plus, you should be able to have the cement blocks filled with insulation which should help the overall performance of the house.

A lot of dormered-0out old-school framing is FULL of these thermal-bypass wind-tunnels. If you have access you can do a lot using corrugated cardboard & staples as custom-scuplted air-barriers, foam-sealing & caulking as you go. (My place had a huge 6 inch x 15 foot communication path below a structural beam between the kneewall area and the porch roof area that was treatable corrugated & blown cellulose.)

Finally had time to start addressing these issues. Had a spray-foam (closed cell) guy out today who said he can, with removal of the soffit and fascia boards, seal up all the joist bays at both ends. (there is NO insulation or barriers in the bays and the bays are directly open to the soffits.

Then we talked about the rest of the roof. Since it's all finished upstairs with limited access to the roof rafters, he said it would be better to wait until the roof needs redoing, then pull up the roof decking, apply spray foam against the drywall, then put the decking and new roof on. If that can't be done, he would attempt to fill in all the spaces in the roof rafters and the attic cavity (about 12 inches height, which includes the depths of the roof rafters and ceiling joists) with blown-in cellulose.

I then called a roofing company and asked about removing the decking for spray foam, and they said they could put rigid foam (about 3-4 inches) *over* the existing roof, then lay a new roof on top of that.

Is one way better than another in terms of energy-saving, (foam & cellulose in the existing roof OR rigid foam and a new roof on the exterior surface) or does it really boil down to price?