Attic fan removal prompts more questions

Q. I have read your column for many years and have learned a lot about many different topics. I now find myself with a question I cannot get to the bottom of, so I am turning to you for your opinion and guidance.

I have a ranch-style home that was built in the late 1960s. Recently I have been approached by two different contractors touting the energy-savings benefits of making my attic unvented by closing the ridge vents in the roof, removing the attic fan and closing the resulting hole, spraying the rafters (underside of the roof deck) with 5 inches of open cell spray foam insulation, as well as sealing off the soffit vents with this same spray. They also proposed 2.25 inches of closed cell spray foam insulation on my basement sill plates.

Do you agree with closing the ridge and soffit vents and eliminating the attic fan? They claim this will significantly reduce air infiltration into my home and save loads of energy, but I am concerned about what might happen to my rafters, sheathing and asphalt roof shingles by cutting off the air circulation in the attic.

They told me by creating an unvented attic, the temperature would be about 5 degrees hotter than the living space in summer and 5 degrees cooler than the living space in the winter.

My attic has two layers of fiberglass insulation between the floor joists. I estimate that each layer is about 3 to 4 inches thick. They told me this insulation is not doing anything and is worthless.

I have been unable to find any independent information regarding this procedure, although I have found quite a few articles on the internet about creating an unvented attic by using this spray foam technique. Unfortunately, all of these articles are by contractors that provide this service or by spray foam manufacturers.

What are your thoughts on this process and would you recommend it for my Mid Atlantic climate?

A. A 1960s ranch may greatly benefit from a number of measures to improve its energy efficiency. But there is something missing here.

Did these contractors conduct a thorough assessment of the air infiltration of your house by means of a blower-door test and infrared thermography? If not, they are selling you a job you may not need for your attic and that may not be as effective overall because nothing is proposed to find the areas that may need corrective measures.

I am aware of the practice of making an attic unventilated by spraying foam onto the roof sheathing - and sometimes the rafters, but I am not in favor of it. And it should not be done with open cell foam insulation, known for absorbing moisture.

Most shingle manufacturers warn against this practice because a lack of roof sheathing ventilation is prone to cooking the shingles, shortening their life. Some manufacturers say that doing so voids their warranty, granted that warranties are often worth very little.

Sealing the attic with foam insulation is not solving other sources of energy loss, so it's only a partial solution that is not the best way to deal with the need for more attic insulation. But it is a way for some contractors to make a lot of money off homeowners.

I always recommend the removal of attic fans, known to be energy-wasting appliances, as they generally rob the living spaces of conditioned air because there usually is not enough net free ventilation in the attic itself to satisfy their CFM (cubic feet per minute) rating.

I always recommend that attic ventilation be accomplished naturally with a combination of full-length soffit and ridge vents and a clear space between the two.

The contractors' comments that your fiberglass insulation is worthless makes them suspicious right off. Fiberglass insulation has its problems, but it certainly is not worthless. It has been around for years and it has done a good job.

Adding 8 or more inches of blown cellulose over the fiberglass insulation on your attic floor may considerably reduce any air infiltration from the conditioned spaces below because of its density - if you do have such a problem to start with (the blow-door test will point out any air infiltration spots) - but make sure the selected insulation contractor protects your soffit vents - you do not want those blocked off, as they are an important part of the ideal attic ventilation system.

This would be far less expensive than foaming the roof deck, and it would preserve the ideal ventilation you now have.

As to the basement sill plates, their suggestion is good, but, again, there are much less expensive ways to control air infiltration in this location. Caulking of the joint between the masonry foundation and the wood sill plate would take care of any air infiltration problem at this joint. Two-inch thick rigid XPS or polyiso foam fitted against the rim joists between the floor joists, with its perimeter caulked, will take care of making this weak band more energy efficient.

Q. My garage floor near the outside door, about 8 inches into the garage, is flaking like sand, and when I sweep it up, the floor is pockmarked underneath. Am I now getting water under the garage floor (concrete) or do I have another problem?

A. How old is the concrete garage floor? I assume this is rather recent development, and because the damage is limited to a small area, it is unlikely the problem is due to errors in the finishing of the garage floor. It points to salt damage.

Have you used salt on the driveway to clear ice? If your driveway is not suffering from the same fate, it must be asphalt, which is not affected by sodium chloride.

The damage can be repaired with one of the many concrete repair products on the market. If you are not able to do the repair yourself, a concrete or masonry contractor is the person to call.

This was forwarded to me: "I never heard of a AFCI circuit breaker so I did some research. There is a website, www.afcisafety.org, that covers it all. According to the article, a vacuum cleaner or furnace motor should not trip a AFCI. Sounds like the person having trouble has a faulty AFCI. He should try another brand of circuit breaker. Please pass this along to Henri. I always read his columns! Thanks."

A. Thanks, and I am passing it along, hoping the reader with the problem AFCI sees this and will have his or her licensed electrician look into this.

• Henri de Marne, a former remodeling contractor turned columnist and consultant, is the author of "About the House with Henri de Marne" (Upper Access Publishing). He continues to take questions from readers for this column and his website, www.henridemarne.com. Email questions to aboutthehouse@gmavt.net.