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attic ventilation/insulation


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I bought an old Victorian home (1889) in southern Ohio about 18 months ago and have done some extensive renovations before moving in about six months ago. The focus before moving in was the living areas. Major work included three new bathrooms, a new kitchen, and new HVAC throughout. The home has approximately 4200 sq feet (livable).

I need to do something in the attic. The attic space is huge and is accessed with a regular staircase and a fullsize door from the second floor. The roof is 9 years ago and shingled. The structure is wood frame. It is feasible to have a decent half court basketball game up there.

It has only been used for storage. The entire floor is planked with what appears to be loose insulation underneath. There are three pairs of double hung windows (very inefficient) and absolutely no other venting. I would like some feedabck on the best way to insulate/ventilate the space. In the near term my priority is be more efficient and less wasteful. In the long term I would consider adding a living space up there.

I appreciate any feedback.

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Probably the best thing you can do is remove the planking temporarily, remove the insulation, air-seal the entire attic floor very carefully, then re-install insulation (probably more than was there, I would go with 20" of cellulose) and re-establish the planking as needed.

You will probably need to build up the framing so that the planking is above the deeper insulation--in my attic I built some simple 2x4 "ladders" and laid them on their sides across the joists, then put plywood over that for a storage floor. Here's a lousy pic... these are 15" high and 24" on center and I laid 8' ply across them. There is cellulose right up to the bottom of the ply.

If you have access to bring in long I-joists, that is quicker and I have done that when we had room to shove them in through a gable opening.

If you do the air-sealing right, my opinion is that you can ignore the attic ventilation AS LONG AS YOU MONITOR what is going on in the attic down the road. You need at least one good hygrometer to do this. Check for dewpoint conditions at various times of the year, starting right away. If you have too much humidity, then you need to cut in more ventilation somehow.

If you're not going to do the air-sealing and put in knee-deep insulation, I would do nothing, as any less won't do you any good.

If you ignore your attic and then go in there five years later and find black stuff growing... not my fault.

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Thx David...I assume air sealing involves insuring that all access is sealed from the livable space below?

Would you see a need to replace the windows? They are floor level.

Also, I can access gables at the peak. It appears that previous owners just boarded the gables. Would you vent these?

Any power ventilation?

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Update the first story ceiling fixtures and wiring before you build the upstairs living area. You won't be able to get to it later.

To demonstrate this next suggestion, grab paper and pencil. Draw a rectangle within a triangle with one edge of the triangle representing the floor of the upstairs room and the other two representing the rafters. The rectangle within is your new living area. The suggestion is to keep the upper corners of the rectangle at least two feet away from the rafters, otherwise it interferes with ventilation and may make it difficult to pass duct-work, wiring, etc from the first story attic to the second story attic. Extend the new living area ceiling joists to the rafters but correct any sagging in the rafters, if you can, temporarily before you nail them together.

Install a new independent ductless mini-split HVAC system to provide comfort to the new living area, otherwise heat will constantly rise from downstairs and cause problems with elevated and uncomfortable temperatures upstairs.

Make sure the existing downstairs ceiling joists are large enough to serve as floor joists. Check out this online tool: Deflectolator

Marc

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If your plan is to finish that space then you need to insulate the roof and gable ends, not the floor.

I would spray foam the roof deck. 5-6" of closed cell foam will get you into the R-35 to R-42 range and fit within the existing rafters. If the gables are framed with 2x4s fill them up too, for R-28. You could save a few bucks switching to open cell for the walls and not notice too much performance drag at R-15, but cellulose will cost even less for the same performance. The windows will provide all the ventilation you will need until you replace them with efficient units. If your new HVAC scheme wasn't designed to handle the extra thousand or so square feet you just added, you can address air exchange when you design the HVAC fix.

If all you want is storage, Dave's plan is brilliant. You won't get a better bang for your buck.

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Tim, air-sealing means foaming/caulking or otherwise sealing all air openings from the main living space into the attic--around pipes/wires, soffits, interior wall top plates, everything you can find. It is easiest if you hire an insulation/home performance contractor with a blower door and an experienced crew. Your access door would become an exterior door and the stair area (walls, under-stairs) would need insulating.

Marc and Tom are correctly pointing out that you would never do what I describe if you want living space. I'm talking about putting the attic fully outdoors because you don't want to heat it or deal with moisture issues.

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Thx Tom, Do I need to worry about venting at the higher end, i.e. gables, peak, etc?

Not with closed cell foam.You could re-frame the space to accommodate a vent scheme and get the R-value with a cheaper insulation, but you'll loose space and probably spend more.

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Because you wrote that the windows are sitting on the floor, be sure to use safety glass. They also need to be sized right for egress in case of a fire, which means you may need to go with one large window instead of two.

What the others have said about closed cell foam should be all you would need for insulation.

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Tim, air-sealing means foaming/caulking or otherwise sealing all air openings from the main living space into the attic--around pipes/wires, soffits, interior wall top plates, everything you can find. It is easiest if you hire an insulation/home performance contractor with a blower door and an experienced crew. Your access door would become an exterior door and the stair area (walls, under-stairs) would need insulating.

Marc and Tom are correctly pointing out that you would never do what I describe if you want living space. I'm talking about putting the attic fully outdoors because you don't want to heat it or deal with moisture issues.

This seems like the logical route, since you are already heating 4000 sq ft. If you insulate the floor of the attic, some gable end ventilation might be all that attic needs to keep it healthy. Some air needs to enter the attic at the soffits, so you want to give the soffits some attention. Old houses often get enough soffit venting from cracks and gaps.

Don't install power vents or turbine vents, as they suck too hard and usually end up drawing air in from downstairs and causing problems.

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If they are only contemplating the possibility that they might one day convert that space, or if they know they will but it's not going to happen for many years, I think air sealing and extra insulation is a good choice for now. They'll end up with a snug home and they'll have a good place for some dry storage.

ONE TEAM - ONE FIGHT!!!

Mike

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It's a walk up attic, essentially a partially finished third floor. The house was built to handle that load. I have been in dozens that have been finished of as family rooms, dozens more that have been converted into apartments, and several that were originally finished as servants quarters. As long as it hasn't been molested or neglected, it will be fine.

If he does in fact want a basketball court up there he may need to beef up the floor joists, but the foundation will almost certainly be more than adequate.

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The odds of the foundation in a home of that age being able to support an additional floor are pretty slim.

What's that prediction based on?

30 years of experience in engineering and construction, ICC certification and a Professional Engineer license. I have spent the last 15 years of my life inspecting 100 plus year old homes. The conditions in your market may be different from what I see every day.

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  • 6 months later...

As I get into insulating the roof and other areas I am concerned about the ventilation or lack of ventilation.

As I stated earlier I have three pairs of double hung windows (single pane) that I plan on repairing/replacing. Other than that there is no ventilation...no ridge vent/soffit vents, etc.

What recommendation are there for ventilating this space. The gable ends are very accessible.

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Tim,

If I were in your position, I'd do what David Meiland said. I'll suggest that if you sheath the "ladders" with plywood, you'll create a very sturdy floor/ceiling.

If you do what he described, you won't need much ventilation - partly because the space is so large.

I wouldn't consider turning the attic into living space. I prefer unfinished basements and unfinished attics.

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I appreciate the advice Jim. I guess what I am leaning toward is give my teenage kids a place to do homework, watch TV...not so much 'living' as in sleeping, etc.

Is there some middle ground that is acceptable with respect to insulate/ventilate?

I do plan on adding additional loose insulation on the floor.

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