How much to spend on attic insulation?

Q. I look forward to reading your articles each Sunday in our newspaper. However, I have to say, I was disappointed in your recent reply to the question about having two layers of fiberglass insulation between the floor joists in the attic — about 6 to 8 inches total. This equates to an R-value of about 18 to 24 if no air is moving through the fiberglass batts. I am surprised you did not suggest air sealing all the top plates and electrical penetrations prior to adding the blown-in insulation. In Chicago, we recommend R-49 in attics, and this was a far cry from that.

The one thing that really got my attention was your suggestion that rather than spend a lot of money making the attic more efficient, the windows be replaced to reduce air infiltration. I hope you were talking about air sealing the attic rather than saying the windows will stop air infiltration. Yes, it should help, but the cost of new windows has a very, very long payback period, in spite of what the window sales companies tout.

My hope is that you will print a clarification of this answer so people don’t think windows are that “great solution.” I also hope to continue to read your column and learn more about the building science.

A. Your letter shows me you have not read my column regularly enough to see that all your comments have been dealt with many times before.

Over the years of writing this column, I have mentioned sealing any convective paths from the living space to the attic to prevent warm, moist air from creating moisture problems, mold and snowmelt on the roof. I have also mentioned increasing the attic floor insulation by blowing cellulose insulation over the existing insulation, covering the floor joists to reduce heat loss through them if the attic is not used for storage. Where there is an existing floor or where one is desired, I have recommended screwing sleepers perpendicularly to the floor joists and (re) installing a flooring material for storage.

My answers to readers are geared to their specific questions, and there is some concern about the length of both the question and the answer. I simply cannot write a book on all aspects of one question every time it comes up.

As to replacing old windows to reduce air infiltration and exfiltration into the house, the research is clear: More heat is lost around old windows, especially in two-story houses, than is lost through inadequately insulated attics.

Q. I read with great interest your recent column regarding vinyl residing for a 35-year-old house. Ironic, isn’t it? I’m looking at some of the same products as were noted in your column.

My home, now also 35 years old, has an older solid vinyl siding that my wife is tiring of, and it is getting more than a little fragile in places. This siding was put on over Masonite siding with an aluminum foil barrier behind the vinyl. Over the years, moisture got behind the siding and caused the Masonite to swell and make waves in the exterior vinyl.

Twenty-two years ago, I was convinced by the installer that the siding could be installed over the Masonite with no bad result — ha, ha! This was a terrible mistake.

Installers I talk to now suggest that I have all the old siding and old Masonite removed, then put on something called Tyvek before the new vinyl is installed. Is this what you’d recommend, as well?

A. Masonite was the first manufacturer of man-made hardboard siding commonly used for decades; it was followed by others.

It is not uncommon to install vinyl siding over hardboard, but success depends on interior as well as exterior factors. The hardboard may have been compromised by moisture permeating from inside the house in the absence of an effective vapor retarder. That moisture may then have been trapped by the aluminum foil — a vapor retarder on the wrong side of the wall in all but hot climates.

It is also possible that, since no siding — especially vinyl — is waterproof, some water may have bypassed the aluminum foil at joints and wet the hardboard siding.

Under the circumstances, it is best to remove both the old vinyl siding and hardboard to get back to the sheathing. Apply a housewrap, such as Tyvek, and new siding.

But now is your chance to also improve the energy efficiency of the shell of your 35-year-old house by installing 1-inch XPS (extruded polystyrene) or polyiso rigid insulation over the sheathing and taping the joints between the panels. In that case, there is no need for housewrap. This added insulation will keep the wall cavities warmer and reduce the potential for condensation on its back side.

Q. Our local historical society owns a boot shop that dates to the early 1800s. The wood of the window sashes has deteriorated and needs to be repaired. We are considering doing the work ourselves and would like your recommendation as to what type of wood should be used for the repairs and whether a preservative should be applied.

A. If the damage to the wood is not too extensive, you may want to consider cleaning out the decaying wood and applying a wood hardener, followed by an epoxy wood repair. Hardware stores and home centers carry such products, one of which is made by Minwax, which is easily worked with common tools and sanding.

If the wood is beyond repair, to stay with the original, pine is the wood to use. It is easy to work with. You should apply several coats of wood preservative before applying an alkyd primer, followed by two coats of a top-quality acrylic paint. Special attention should be given to sealing the joint of wood to glass with the paint.

Q. I live in a two-story house. In the winter the second level is cold; currently, in summer, it is hot. When you get to about the 10th step up, you feel the heat. The main level will be fine, while the upstairs is very uncomfortable. It is about 8 degrees warmer on the second level.

Is this an issue with our attic insulation? Air conditioner? I would like to know how to start getting this problem fixed.

A. It is normal to have some difference between the main and upper levels of a house because warm air rises. But in your case, it does sound as if there is considerable heat loss through the attic since the second level is colder in the winter when it otherwise would be warmer. Have you noticed rapid snowmelt and ice buildup at the eaves of your roof? This is a dead giveaway.

Inadequate attic insulation and possible convection from the heated space will cause excessive heat in the level below the attic. Heat loss through an attic folding stairway or access panel also can be responsible for a second floor that is cold in winter.

Consider having the attic insulation level checked and improved, if need be, by blowing cellulose over the existing insulation. To determine if convection of warm, moist air is also responsible for the winter problem, consider having an energy audit performed. If problems are found, they can be sealed with canned foam and the level of additional insulation recommended.

These steps will help not only in winter but also in summer, as high levels of added insulation will reduce the heat transfer from the attic to the living space below. You also should have an experienced HVAC (heating, ventilation and air conditioning) contractor check out your system. It may need some adjustment to bring more heated and conditioned air to the second floor.

Q. We recently purchased a new home, and we are finally ready to paint and put up some decor. The reason we waited so long, especially to paint, is that we have four small boys, and the walls are constantly being scratched up. Knowing this, I was wondering what the best kind of paint would be to buy. Once we do paint, how would I go about wiping the walls if, by chance, one of the children accidentally scratches them up?

A. If by “scratches” you mean actual physical damage to the walls, I doubt that any regular paint would be able to stand up to the test.

But if you are referring to children’s “artwork” with crayons or paints, a high-gloss paint would be best and can be easily wiped. The downside is that it will show any irregularities on the wall and will be quite shiny. The second choice would be a top-quality paint in a satin finish, which would still be easy to wash clean of any “decorations.”

The “artwork” can be wiped off with any nonabrasive, gentle household cleaner, such as 409.

Q. We saved your information about staining a pressure-treated deck. You recommended Wolman products. Do you know where we can find them? I’ve tried Lowe’s, Home Depot, Sherwin-Williams, Aubuchon and no one has heard of this product. Is there another stain you would recommend?

A. I am surprised you have met with such lack of success. Wolman products are widely sold in lumberyards, paint stores and some hardware stores. I’ve sent you the names of a few businesses in the Vermont area where you live that carry Wolman products. The company is owned by Rust-Oleum. To save yourself a wasted trip, call to find out if they have these products in stock.

Q. Your recent comments regarding roof moss and Z-Stop confuse me because they conflict a bit with the info on the company’s website (www.z-stop.com).

For example, you say there is no need to power wash, pre-clean, etc. The website says power washing and pre-cleaning are necessary to get rid of existing stuff. Can you clarify? Also, it would be helpful if you have a list of suggested contractors who specialize in this work. Otherwise, I find your advice helpful in many ways.

A. I am aware that several sites erroneously recommend power washing roof shingles, but they ignore that doing so runs a serious risk of dislodging the mineral granules that protect the asphalt matrix of both organic and fiberglass shingles.

Highly experienced contractors specializing in roof cleaning (mostly found in the humid Southeast) will power wash wood, tile and asphalt roofs, but they know how to adjust the pressure to avoid damage. My concern is that I am advising homeowners and nonprofessional contractors who do not have that experience.

Some manufacturers also claim their products will clean a roof in a few days, but the results are not always satisfactory. Zinc strips will do the job over time and keep the roof clean for many years.

Roof-cleaning specialists are found in certain areas and should be listed in your Yellow Pages.

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.

© 2012, United Feature Syndicate Inc.