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posted: 2/2/2014 12:25 AM

Old concrete may have been attempt to trap air bubbles

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Q. I have a friend who purchased a house that had been built in the 1940s or '50s. She is now having the bathroom completely "gutted" and in this process, the contractor/carpenter had to rip out all but the studs. He told her that behind the existing walls in the shower area the original builder had put metal shavings (wire) with concrete then poured over this wire. He had to charge her for three extra hours as it was quite a task to remove the concrete. He told her the good news was that he found no mildew, as this was something she feared might be going on.

Coincidentally, this past week another person told me that a house that my uncle had built in the '50s -- and that my neighbor has purchased -- had the same problem. He wanted to renovate the bathroom and found that behind the studs the wall was made of concrete.

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My question is, was concrete found at that time to be a good insulation? Or did it have something to do with avoiding mildew?

A. This is very interesting, as it seems to have been done in the 1950s before Air Krete was developed. Air Krete is a very effective insulation, which I believe came on the market in the late 1980s. Air Krete is a modified oxychloride cement product that is formed of air bubbles encased in cement. I used it in a house for a friend as a repair product. He built his house with precast concrete panels, which had developed many gaps between the panels. We had Air Krete injected by a licensed contractor into all the voids. It worked very well.

Regarding the two houses you are referring to, I can only wonder if some clever contractor had this technique figured out at that time.

Concrete per se is not an insulator. An 8-inch-thick concrete wall has the U-value of a single piece of glass. For example, it takes an 11-foot thick concrete wall to equal 3 inches of fiberglass.

Q. I had an air conditioner on a dormer window of the pitched roof of my Cape Cod house that leaked rusty water onto my gray asphalt roof and left stains. I tried to hose it down really close to the stains, but that didn't help. What do I use to remove it? Any ideas? I wish I could take a picture, but the snow is in the way.

We do have extra shingles that we can try something on, so as to know that what we use won't discolor the shingles.

A. Try the following: Mix oxalic acid crystals to saturation in hot water (saturation is obtained when some crystals can no longer be absorbed). The proportions are one pound of crystals to one gallon of water, but that is probably too much solution for your rust stain, so adjust it accordingly.

You can purchase oxalic acid crystals from some paint stores or janitorial supply houses. Be careful handling oxalic acid as it is caustic. Wear old clothes, skin and eye protection, and use a plastic or glass container. Do not use metal containers or tools.

Using a plastic garden sprayer, spray the stained area and let the solution stand for 15 to 20 minutes. Rinse with your garden hose.

If this is not successful, repeat and very gently scrub the affected area with a soft bristle brush in order not to damage or dislodge the mineral granules that protect the shingles from the sun's rays.

Q. Last year, I purchased a 95 percent-efficiency Lennox gas furnace. When I used high-efficiency filters, the furnace made banging sounds during its startup and shutdown. I notified the installer; he had no idea how to rectify this problem. However, I replaced the filter with a low-efficiency filter (a remedy action taken by chance) and the noise stopped.

I read your column on how to reduce dust in house using high-efficiency filters. What is my solution?

A. It sounds as if the restrictive airflow through the high-efficiency filter caused a negative pressure in the duct system, which resulted in the ducts buckling. When the furnace turned off, the pressure equalized and the ducts returned to their normal static state.

Q. My wife owns a 100-year-old-plus building (in Toronto) with a store downstairs and two apartments above. She has had a persistent problem that none of the people in these parts seem able to really solve. The downspout at the back of the building develops a huge, thick coating of ice in winter and water pours down the back wall in summer when it rains. I've attached a couple of pictures to show you the situation.

A. Thanks for sending the photos, but I am not clear about what I see because the entire area is covered with this huge ice mass. You certainly have quite a problem.

For so much ice to develop, there has to be a massive heat loss through the roof. So the first thing you should tackle is what to do about it. Canada has excellent resources in the home energy field, including some top scientists who are internationally known. You should be able to get help from the government or utilities. The Internet should be able to direct you to these resources.

It seems to me that an energy audit is advisable, followed by corrective action.

This would address the winter ice problem, but the summer one -- water pouring down the back wall -- would indicate a roof discharge problem. The downspout may be too small for the amount of water collected by the roof area; there may also be a problem with either gutters (if there are any) or other means of directing water to the downspout. An experienced roofer should be able to see what the problem is and to correct it. But if not, a professional engineer would be the person to call.

I hope this helps and I wish you both a quick resolution to this potentially serious condition, which may lead to structural problems.

Potentially lifesaving advice: A recent tragedy compels me to write this. A family was away over the holidays. A neighbor was keeping an eye on their house and taking care of their pets. A power outage caused by ice knocked out the power in their neighborhood, and lasted several days. As I understand it, the owners asked the neighbor to light their wood stove to keep the pipes from freezing, which the neighbor did. A chimney fire ensued and the house burned down to the ground.

Wood stoves can generate a lot of creosote, the amount depending on the care of the wood being used, the way the stove is managed, and the regular cleaning of the chimney. It is possible that some or all of these cautions were not observed.

There is a product that has been available for many years and which should be used daily in all wood stoves: It is ACS, the acronym for "Anti-Creo-Soot" developed many years ago by a chemist whom I had the privilege to know and work with. ACS is a catalytic solution that changes the chemistry of the wood-burning gases. Instead of these gases attaching themselves to the walls of a chimney and turning into glaze creosote -- a highly flammable coating -- ACS catalyzes them into a very fine brown ash that is easily cleaned with chimney brushes. Chimney sweeps love ACS, as it makes cleaning chimneys easy when compared to the often futile and always difficult job of dealing with Type III creosote.

ACS can be sprayed on the logs while in storage or as they are introduced into the stove. Having used wood as my sole source of heat for decades, and cleaning my own chimneys with the appropriate size chimney brushes, I can vouch for the efficacy of ACS.

Everyone burning wood should use ACS religiously daily. You can buy it online at Amazon.com or from www.chimneysaver.com.

Follow-up from a Williston, Vt., engineer: In response to my answer to a reader who had found a lot of water in his dishwasher after it had run through its full cycle and was upset about the absence of a heating element in the dishwasher, I received the following email:

"Please allow me to explain about the case of the dishwasher that does not have a visible heating element.

These dishwashers (I know LG also makes such a product) require the use of a surfactant (rinse agent) -- e.g. Jet-Dry. The rinse agent, which lowers the surface tension of the water, allows the glassware and dishes to drip dry enough such that the residual heat (from the hot water) is sufficient for the load to dry. If a rinse agent is not used, there is so much water left on the contents that there is not enough energy from the residual heat to evaporate all the water.

This process is far more energy efficient, thus the push for this type of feature. I have personally verified this with my son's LG unit (being the engineer that I am). In fact, upon witnessing this, I have since stopped using the "heat dry" cycle of my KitchenAid brand machine and found the results amazing (yes, I have been wasting energy with the "heat dry" cycle for years). Please spread the word."

A. Done and thank you for the explanation.

• 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.

2013, United Feature Syndicate Inc.

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