Just wanted to share my experience. Shortly after I moved into my well-built 1973 home, I had a door-blower test performed by a friend. So not a full work-up, but we walked around and felt all the drafts. The previous homeowner was somewhat of a DIYer, and had done a good amount - sealed the rim joist with thick beads of serious caulk. Added r-19 to an r-19 cellulose attic (r-38 total). Good weatherstripping. Etc.
So we found moderate leaks. All the cans/recessed lights leak like crazy - I'm going to build custom foam boxes to put around them and seal to the top of the drywall for those. Gives them airspace inside the foam, but makes the cans air-tight and adds some extra insulation around them. Simply take a piece of thick foam and cut it into a ~10x10x10 box pieces. Caulk the pieces together. Then put it over the can in the attic. Then caulk the bottom to the drywall. Then lay your fiberglass on top of that. Takes maybe 10-15 minutes per can.
Improved sealing to the attic and main wall spaces.
But what I missed from that test was the very broad amount of air being lost through the baseboards. Which has now been fixed via additional caulking and a foaming and tyveking of the entire exterior. Simultaneously, the entire house got a thermal bridging break through the addition of 3/8" fanfold foam put under the vinyl siding.
One thing I'll add to that is that most people don't know what their house is currently sheathed in. I had cement fiber siding. It was attached to the house via furring strips. Which were mounted on the original house sheathing - treated external sheetrock. Well, after 35 years that sheetrock was crumbling and full of holes. So all my rooms had air gaps coming in up under the cement fiber boards (which had 1/2" gaps under them) then up around sheetrock, down the walls, and through baseboard trim.
One other thing was that the main vent pipe running through the attic was completely unsealed. Probably 1 cubic foot around it. Was just stuffed with insulation. Massive heat loss spot right in the center of the house and since it's a main pipe - it's getting massive stack effect. A simple foam board cut-out, some more caulk, and the air is either eliminated or massively reduced.
What I notice now is that if I close my master bedroom door, even with a ceiling fan on (but not the central air/heat flow), the air gets stagnant. It's uncomfortable.
What this is telling me is that my interior air-flow is now getting vastly decreased. Probably to the point I want to stop air-sealing - since in the winter I might have my furnace AND wood burning stove on at the same time.
Next then is radiant heat. For me, that's the garage which butts up against conditioned space on 3 sides - my main living space on one side, a bedroom above it, and my foyer area butts the back of the garage.
I don't know if I can get away with it, but I'm planning on using some sort of foam sheathing there to add r-6 insulation + vapor barrier + thermal bridging.
Anyway, I noticed a marked decrease of my A/C bill this year and my siding was doesn't until August. What this tells me is that these things are already making a marked difference.
We'll see how my heating does this winter - I've made alot of large investments, so it's time for them to start paying off.
