Home repair: Be cautious when insulating basement walls

Q. I am about to finish my basement in a home built in the 1970s in the West Chicago suburbs. I have the following question about vapor barrier and insulation in the stud walls against poured concrete basement walls.

In your book “About the House,” published in 2007, you recommend plastic barrier between the insulated studs and the drywall and putting the insulation only from the top to within 2 feet of the basement floor. Great book, by the way.

In Roger German’s book “Remodeling a Basement” (Taunton Press, 2010), he makes no mention of stopping the insulation 2 feet from the floor, but he makes the following comment about plastic vapor barrier, referencing recent Building Science Corp. reports: “Basement walls insulated with vapor barriers applied in the old approved manner have been found to be damp because of moisture trapped in the wall cavity that migrated in from the outside, or from infiltration from the inside. It seems that air infiltration is an even greater problem than vapor migration, and there is additional moisture wicked up through the footings and the foundation itself. It is better to omit the vapor barrier altogether. Just frame the basement walls next to exterior walls as we describe in this chapter, but simply don’t install a vapor barrier.” I would appreciate your thoughts on what he says here about no vapor barrier.

In your book, you differ on having insulation go all the way to the basement floor, saying it’s OK in light soil but should go only to within 2 feet of the floor in “heavy soil.” How do I know what I have?

One of the items I have picked up on that is confusing is “fire blocks” requirements. No book or site I can find explains it well, especially in reference to International Building Code (IBC) requirements. I know they mean you should put a wood block about halfway up the stud wall — easy enough to understand. But, for example, the kind of fire block that is needed when building a soffit next to a wall to cover a heat duct is hinted at often in some books I have, but I can’t find any book or website that really explains and shows it with any clarity. Do you have a suggestion for a website or book that would decipher and give basic, clear information on such IBC codes for a basement project?

A. Sorry, but my recommendation is to insulate only down to 2 feet below grade — not 2 feet from the bottom of the wall (page 335).

The problem I see so often with authors who advise how to insulate basement walls is that they do not seem to take into consideration the soil conditions. I wonder whether these authors have had practical construction experience, or simply work in theoretical realms.

You will find in my book, and in all of my writings, that I distinguish between the type of soil and backfill around a foundation. If the soil is gravelly and coarse, or if the backfill was made with such soils, it is quite safe to insulate all the way to the basement floor. But in case of uncertainty, the insulation should be carried only from the ceiling down to no more than 2 feet below grade. This allows some heat conduction into the lower soil to prevent deep frost penetration that can, and has, cracked even concrete foundations. The top 2 feet of the soil is the most vulnerable to heat loss anyway.

If you insist on insulating all the way to the floor, the only way to tell what kind of soil you have is to dig in several places. You’ll have to go 2 feet to 3 feet down to determine whether well-draining backfill has been used.

The best way to insulate basement walls is to use rigid insulation sheets as shown on page 335 of my book. When applied against the walls, they eliminate much of the risk of condensation and, since they do not absorb measurable moisture, the problem alluded to in the Building Science article you mention, is all but eliminated.

I do not know of any literature dealing with fire blocks at soffits in basement finishing.

Q. A heating/plumber friend offered to come and look at my HVAC system. He said it was installed very poorly and he doesn’t think it will ever pass inspection. Because I don’t have the money to replace the whole system, he suggested I have him put in a Tjernlund duct booster as a way to send out more heat. What do you think?

A. It’s worth a try. Is he planning on installing only one? (You are using the singular.) Did he tell you how he is going to install it and the cost? Let me know how it works for you.

Q. Our circa 1840 home has a basement made of fieldstone with little or no mortar, which has not leaked in the 10 years we’ve owned the house. During the heavy rains this year, there has been substantial water intrusion in the basement, together with a lot of fine sand that appears to have washed through the spaces between the stones. (I removed 10 five-gallon pails of sand.) The leakage was confined to one corner of the basement. I have regraded the area outside this section and chinked many of the obvious spaces with Drylok cement, but the problem persists. What should I try next? Do you know of a product that could be sprayed or painted on the cellar walls to eliminate the problem?

A. Since you still have the problem, you should check the grade farther away, as water can travel in unsuspected ways. Sorry, but I don’t know what else to suggest besides doing more with the Drylok, as it is practically impossible to waterproof foundations of fieldstone laid dry. Grading is almost always the best way to control and eliminate foundation leakage.

The 50 gallons of sand you removed came from somewhere and may have left some sizable voids, which may be responsible for the continuing leakage. If at all possible, you should try to find out where the sand came from and put it back. Tamp it down as much as possible.

Q. The contractor who built our house is now dead. The roofer who applied the replacement shingles has the telephone message, “The person at this telephone is not accepting calls.” We have found a craftsman who climbed to the roof, did an inspection and took some pictures.

One photo shows the roof above the area of mold. A second photo shows one of many areas where the cap has lifted from the ridge vent.

The craftsman says he cannot see where the ridge vent connects with a vented space over the structural insulated panels. Another photo shows where the roof of the cathedral ceiling connects with an adjoining wing of the building. There seem to be soffit vents present. I suspect that our craftsman is mistaken.

These findings seem to explain the mold on the ceiling below but may not be the complete explanation. When cold weather comes, we will proceed with the energy audit you have recommended, which is a good thing in any case.

A. What a thoroughly messed-up situation you have been left with!

Indeed, there is no opening at the ridge for any ventilation. The question is whether your SIP panels have ventilation slots built in, as some do. If they do, there should be a ventilation slot across the ridge for the ridge and soffit vents to function as intended. If the SIP panels do not have ventilation slots, both soffit and ridge vents are useless.

It seems to me that you have had two incompetent contractors: the deceased homebuilder and the roofer who replaced the roof later. No wonder he won’t accept phone calls! His work is appallingly sloppy, and that’s his way of avoiding complaints.

Hopefully, the energy audit will help you sort this mess out and will offer some practical solutions.

Q. We have a home built in the 1950s, and we have made a lot of improvements since buying it. However, the windows are not energy efficient. At an energy audit a few years ago, we were told that at our age (in our 70s) it wouldn’t pay us to replace them. We have been using plastic on the windows in winter to keep them from frosting up and sweating, but I don’t like the look when the plastic is on, and it is a pain in the neck to put up every year. I recall reading something once about reusable clear panels that I believe cling to the windows as a type of insulation in winter.

If this sounds familiar, do you recommend using them? If so, do you know a brand name or company that sells them? I have no idea how expensive they are, but even buying tape each year is costly, and it doesn’t always stick that well.

A second question that isn’t as important, but more a frustration, is that our white kitchen range has yellowed near the oven steam vent. I’ve tried various cleaners, but nothing seems to remove it. Any suggestions?

A. The energy auditor advised you on the basis of how long he or she thought, or was told, that you would stay in the house. The advice is also based on any other improvements you have made. Windows are a great source of energy loss, but replacing them at a high cost may not be worth it if the walls have no insulation, especially if your house is a two-story one. The entire picture needs to be evaluated before embarking on costly improvements.

I have mentioned several times in the past the great job Magnetite storm windows do. They were originally developed by MIT. Magnetic tape is applied to the window frames, and the metal frames of the acrylic glazing panels stick to the tape and provide a tight seal. We have these storm windows on our old casements, and they are a great help.

The yellow staining may have affected the enamel deeply, but in case it is only a surface problem, try bleach on it. First try the type you may have in your laundry. If that does not help, you may want to try an oxygen bleach such as OXY-Boost by Pacific Sands (www.ecogeeks.com). If the stain is on a vertical surface, you may need to add OXY-Cling to allow it to stick longer.

Q. How can moss be removed from an asbestos shingle roof? The roof is about 40 years old and is in good condition otherwise — no leaks or other water problems. Trees have been removed, and others have been cut back. The moss is quite heavy.

A. Try either Spray & Forget (www.sprayandforget.com) or Wet & Forget (www.wetandforget.com). Both claim to be environmentally safe, and readers have reported good luck with both. As with all products and methods of dealing with moss, lichens or algae, you must follow directions on the containers and allow plenty of time — sometimes months — to see results, depending on the extent of the infestation.

Another choice is an old remedy: Mix three parts white vinegar to one part water and spray it on the growth. It will also take time to get results.

Installing zinc strips just below the ridge cap shingles will keep a roof clear of these growths. You can buy them at www.stainhandler.com.

Ÿ Henri de Marne was a remodeling contractor in Washington, D.C., for many years, and is now a consultant. Write to him in care of the Daily Herald, P.O. Box 280, Arlington Heights, IL 60006, or via email at henridemarne@gmavt.net. His book, “About the House,” is available at www.upperaccess.com and in bookstores.

© 2011, United Feature Syndicate Inc.