Tighten Up This “Old” House
Oh my! After reading the wealth of info on this regarding good building practices, air and vapor control I am no longer sleeping at night thinking about my house. Are there any actions I can or should take to tighten this house up a bit? Here is the baseline and a couple of observed problems.
Location is Southern N.H., zone 5a I believe as we are 60 miles NW of Boston. House is a 2 story hip roof colonial of 2900 sq ft built in 1988 in accordance with the building codes at that time. The house was under construction when we bought it so I know the ugly details of it’s innards and have been a victim of its sloppy “craftsmanship”
Situation 1:
Wall construction – from the outside-in. Cedar clapboard, OSB sheathing, 2×6 framing, fiberglass batt insulation, 6 mil poly “vapor barrier”, wallboard and high quality latex paint. No, I didn’t forget anything. There is no housewrap, not even around the window openings. Window casings nailed direct to sheathing and siding butted to casing, that’s it. Z-flashing was used over the top of windows and doors. Oh, except they forget the flashing over the front door. I had to replace that door and sheathing on both side about 10 year ago. I have had a couple of other places where I have replaced siding/sheathing but I found long ago that the secret to keeping this house standing it to keep the caulking in meticulously perfect shape, tight as a boat or pay the consequences. From the outside, what else can I do? from the inside the wallboard is cold around the windows. No doubt there is an insulation gap in the rough opening. How to tighten that up? I have sealed up as best I could all through-the wallboard protrusions such as electrical outlets and switches, etc.
Situation 2: I have a walk-up attic. It is very well ventilated with continuous soffit vents and ridge vents. I had a real craftsman re-shingle the roof and he put the soffit vents in as part of the work, replacing the old Hicks vent style that was integrated into the drip edge. This attic stays as cold as the outdoors and never has ice dams, even with gutters. The attic was built to be expandable to another room which I will never do, so it has 2×10’s for ceiling joists, blown-in fiberglass insulation, no vapor barrier in the ceiling. Most of the attic has T&G sub-flooring. So that limits the insulation to joist depth. The part of the attic that has an open floor has insulation a couple of inches over the joists. There are no ceiling mounted lights on the second floor, bathrooms have fans that exit outside. Here is my concern. I had occasion to pull up some attic flooring to access electrical work. The bottom of the plywood was stained black, looks like mold but was also dry and nothing flaky. The joist were clean and solid. Never any moisture on the inside of roof deck (also OSB) either. I have repainted over the last 5-6 years all the second floor room ceilings which were the original builder paint. We store a lot of boxes and clothes in the attic and never have had any dampness, mold, mildew. Should I be concerned about what I observes with the flooring, and if so what course of action should I take?
Thanks for reading all this,
Sleepless Ted in N.H.
GBA Detail Library
A collection of one thousand construction details organized by climate and house part
Replies
Ed,
My condolences.
The easy one first: I wouldn't worry about your attic subfloor. The subfloor occasionally gets damp, for all of the reasons you understand -- moisture leaving your house via air leaks, and accumulating on the cold subfloor -- but it dries out quickly. The problem can be lessened by performing air sealing work at your ceiling level -- you probably have air leakage at the cracks between your partition top plates and your partition drywall -- but that work is difficult in light of the existing attic flooring. So I would put that issue on the back burner.
Of course, if you have a walk-up attic, it's possible that your attic stairway has terrible air-barrier continuity issues and thermal barrier continuity issues. I hope the door to your attic is a weatherstripped exterior door. I'll leave it to you to worry about the details in the vicinity of your walk-up attic stairs.
The fact that your house has no water-resistive barrier (WRB) and bad window flashing details is a huge problem. Your walls have air leaks, and rain has already rotted some of your wall sheathing. This issue needs to be addressed over the coming decades.
Caulking is no solution. In fact, caulking can make this type of problem worse, by trapping moisture in the walls and limiting drainage.
You can address this problem in a piecemeal fashion, as each désastre-du-jour arrives at your doorstep (one soggy emergency at a time), or you can bite the bullet and pay for all of the work necessary to address these problems: strip the siding, perform air sealing work, install new housewrap and window flashing, install furring strips (with or without exterior rigid foam), and install new siding.
Were it not for the slight inherent back-ventilated nature of clapboard siding the OSB might have failed miserably by now. You may have been saved by deep roof overhangs too(?).
It's possible to tighten up the place by blowing cellulose over the batting, but if you have much rain-wetting around the windows the hygroscopic nature of the cellulose might aggravate rather than protect. Dense-packing to 1.8lbs density with fiberglass might be safer, and will definitely slow the air leakage through the walls.
Most homes in this region have a full basement, and NO foundation insulation. From a sheer energy-use point of view, insulating and air sealing the basement walls, foundation sill, and band joist stands on it's own financial merits (especially if you're heating with oil or propane), but doesn't address the resilience issues of the walls on top of that foundation. It will slow the stack-effect drives pushing conditioned space moisture into the attic though (sometimes by quite a bit.) As long as you seal both the top and the bottom of the "stack", you've fixed the first 75% of the 24/365 air infiltration problem. The air leakage in the intermediate floors doesn't matter nearly as much.
Martin & Dana,
Just wanted to quickly follow-up and thank you for your response and input. At least I can take the attic situation of the top of the concern list. The walk-up attic door is an insulated door with good weatherstripping. I replaced the original hollow core door long ago. Insulation up the stairs is good so I am the best shape I can get to at this time with the attic so I'll let it fade off the radar screen.
I will continue to closely monitor and aggressively address the flashing/sheathing/clapboard problems as they come up as the best approach I can take at this time. The problems I have had have all been on the first floor of the house around windows and doors. The upper story seems to be protected by roof overhang & gutters. When I have had occasion to remove siding further away from door/window area's I have always found the OSB sheathing to be in like-new condition. So I guess that speaks to the observation that if it gets wet and can dry reasonably quickly there is a good chance of long term wall integrity.
As an aside, when this house was being built in 1988 with the building codes being used here at that time I had a discussion with the builder about the use of a house wrap and why he wasn't going to use it. He insisted that it wasn't "settled science" so to speak and that house wrap might end up being a double vapor barrier with the 6mil poly. I was doing a corp relocation from a couple of states away at the time and just didn't have the time to pursue the facts and argue with him. My mistake. We're talking 1988 here, not the middle ages. Tyvek or equivalent had been in use for years with no appreciable problems as far as I know. Nothing excuses poor or no flashing at any rate.
Again, thanks fro responding,
Ed
Your house sounds typical of many of the homes in your area built in the 80's and 90's, although the lack of flashing was clearly an error. Early Tyvek had a serious problem when used with cedar siding which was not back primed; the tannins in the material changed the chemical composition of the paper, and prevented the passage of liquid water, so that any leaks caused sheathing and/or siding rot. They definitely should have used something, ideally tarpaper, but their could have been extensive damage had they used Tyvek.
You say you have cold air around your windows; I suggest you carefully remove the window casings, remove any fiberglass, and fill the cavity with low expansion foam. This will require some paint touch up, but can be relatively non invasive. I've seen spaces over an inch wide with no insulation in builds of that era; these air leaks can contribute a lot of infiltration.
In terms of your siding, if you decide to replace the siding, it may well will be worth adding foam sheets to the wall to increase your insulation levels and decrease the infiltration.
Finally, consider getting an energy audit which can identify problem areas in the home and help to identify the most cost effective solutions. there is a list of qualified auditors at REPA-NH.org