See "insulating the outside of a house for insulation/r-values" post regarding direct vent appliances its very important if you are trying to make your house airtight.

Thanks beaglebuddy, I did read that post. It may be more pertinent to the exterior insulation/stucco work I'm also considering in future. For that, as I pointed out in my original post, there is a lot more that goes into insulating and stuccoing an exterior wall. As you know, that aspect has been the subject of divergent theories, extensive research, and a history of failures and severe damages, followed by more research and theories, etc. Do you seal, do you let it breathe and yet provide drainage, etc? I referred to the Mike Holmes' episode which I thought addressed the correct way, and I would follow that process, if I do it at all. I did take note in that post of the concerns re the direct vent appliances balancing sealing of the house. I have electric water heater, but gas fired hot water heating. I also have a woodburning masonry fireplace with chimney. To repeat, that is a massive and expensive effort, which I may never get around to undertaking fully, as it may not be cost effective for the benefits gained.

That post however does not address the venting/insulation work I'm proposing for the soffit, knee wall, attic, etc areas. Relieving the heat buildup at the second floor is more of a priority for me at this time, and I was hoping to get some comments on my proposed solution or other suggestions.

How about a whole house fan to exaust that hot air in the summer, I installed one on our house in Hawaii. It's made by tamarack I believe, very quiet,has insulated doors that open automatically and has been fairly effective.

Beaglebuddy, the whole house fan, or something like that, is a possibility.

I installed a power attic vent in the previous house, and I could do the same here.

I'm also thinking that, as much as open soffit vents, gable and roof vents are beneficial in the summer months, if they were closed off in the cooler months, would that be a good idea? This could be done to a lesser or greater extent with uninsulated or insulated covers or shutters, which could be attached as part of seasonal maintenance, such as with storm windows. The problem would only be if there were significant air leaks which allowed overly humid interior air to escape into the attic.

Ted

Sealing off the attic to the outside in the winter sounds like a good idea to me, I know people in my erea tape garbage bags over their whirly gig roof vents ( a real classy look )in the winter. But there may be pitfalls, perhaps someone could comment ?

I think adding foil sheathing boards to the
2nd story walls to the attic side will eliminate
the heat gain in the summer. If you tape all the
seams you will also be stopping the air movement
in these walls.
The same foil sheating on knee walls (again to
attic side) will benefit you also.
I see a lot of people sealing here & there on
their homes. How do you know where the air is
comming from?? Granted there are times you can
feel a draft, or a breeze depending on how large
the openings are, but it is not a very effective
way to seal air infiltration.
I test homes with a blower door, this puts the
house under a forced negative pressure, measuring
the amount of air infiltration, but also allowing
you to find these leakage sites most effectively.
In older homes it's a crap shoot if you don't know
where & how to seal.
Look for someone to do a home diagnostic for you,
or contact your DOE or DNR (depts of energy or natural
resources) to find someone in your area.
Power ventilators can pull as much conditioned air
from inside your living space through holes & gaps
as they exit from the attic. Add enough PV's
to a leaky house & they keep the house under a negative
pressure. (but hey the attic is cooler...wonder why!)
Best of luck with your project.

The idea behind a whole house fan is for it to be an air replacer. You open a window on the ground floor away from the sun, in the cooler part of the day. The hot air trapped upstairs is replaced w/ cooler outside air.

We have a whole house fan. Not only is the upper floor cool but the attic as well. No radiant heat from the attic in the evening.

I have a recommendation for whole-house fans, and that is to go with the ones made by Triangle Engineering of Arkansas (made in the USA!).

These things move more air than any other brand. As an example: the 36" belt-drive model sold at Lowes & Home Depot moves 6,900 CFM on its highest speed. The 36" one that Triangle makes moves 10,600 CFM.

I just put one of these in last week and am so taken with it that I'm evangelizing for Triangle now.

These things are much higher quality than the other brands too -- these are made with very heavy-gauge solid welded steel (as opposed to the thin, flimsy metal - often aluminum - that other brands use). They use a very solid motor made by Emerson, the best of the top three motor-making companies (the other two being Fasco and A.O. Smith). They come pre-framed on a wood frame for installation, AND they have sponge-rubber noise-dampening material between the fan and the frame, so they are much quieter than the other brands. Also, Triangle holds a patent on an automatic belt-tensioning system these things use, so you don't have to worry about getting the tension right when you install the fan (or in the years thereafter as the belt loosens up).

Also, they come in more sizes than the other companies -- from 24" all the way up to 48" blade diameter (which moves a ridiculously whopping amount of air; no one else makes one that big).

They're sold online at Southern Tool amongst other places that ship nationwide, so they're available wherever you live.

Also, Triangle re-brands some of these as a private label for Dayton, which is the "store brand" of Grainger - so if you have a Grainger store near you (check your phone book or their website), you can buy one there. I will say this, though - Grainger/Dayton makes their own shutters, and those shutters are much better than the one Triangle makes. Triangle makes great fans, but crappy shutters. Luckily, they're sold separately -- so buy a Triangle fan and Dayton shutters; money can't buy better products.

They also re-brand some for a company out in San Francisco called "Fanman" (a/k/a "Delta Breeze").

A word to the wise -- these fans move a lot of air, so make sure to install at least the recommended minimum amount of attic exhaust space (gable vents, soffit vents, roof vents, some combination thereof, whatever works for you) - if you don't have enough, the fan will operate at reduced capacity, and there will be a backpressure which will cause the shutters to rattle when the fan is in operation (any time you hear whole-house fan shutters rattling, you know there isn't enough exhaust space). Oh, and one other thing -- only buy a belt-drive whole-house fan, don't EVER buy a direct-drive model...the direct-drive models are at least five times louder, they sound like standing on an airport runway next to an old prop plane getting ready to take off.

Several of the dedicated whole-house fan installing companies have chosen to use Triangle fans; that should tell you something. These companies want satisfied customers, so they use Triangle and only Triangle.

Refer to http://www.trianglefans.com/wholehouse.html for more info

Here is a link that might be useful: Triangle whole-house fans