Answer: Fiberglass asphalt shingles these days have a limestone filler instead of the traditional rag filler, and the limestone promotes the growth of algae that shows up in horrible streaks on roof areas that don't get much sun. Have your roofer nail copper or zinc strips on the peaks above these areas, so rain running over the strips will kill the algae. Or look into shingles containing copper to solve that problem.
Whatever you do, don't try cleaning the black stains, or mildew, for that matter, with water and bleach. It will reduce the life of asphalt shingles.
Q: The dinosaur in my basement, which so far has heated my house without major problems, is due for replacement.
My dilemma is: oil or gas?
My small, three-story rowhouse is heated by oil. I have no complaints with the companies that provide the fuel oil and the annual clean-out and service contract.
I suppose the thing that gives me pause about staying with oil heat is the crazy spiking of prices over the last year.
The estimates I've gotten so far for installation of an oil vs. a gas system have been about a wash. So for the long haul, which type of system is likely to be most predictable, operating costwise? (Or am I delusional to think either system will ever again be predictable?)
I'd like to hear the opinion of someone who has nothing to gain from my decision: oil or gas?
A: I've had both oil heat and gas heat, and prefer gas because it seems to be cleaner and more efficient than fuel oil. I suppose my view is colored a bit by the memories of my late-October cleaning of my monster in the basement several years back. On the other hand, I do have a gas condensing furnace - check the Internet for manufacturers' explanations. I've had only two problems with it in the last nine years, and both were the result of improper installation by the original contractor 10 years ago and a previous owner. Frankly, the cost of those repairs was well worth it, considering that I ended up with a reliable servicer.
I don't know anyone who has ever succeeded playing the gas vs. oil price game. I think the key to your decision is the efficiency of the furnace you buy and the warranty and service provided by the installer and the manufacturer, and not trying to second-guess OPEC.
Q: We live on the ground floor of our house and use the upstairs bedrooms and bath only when we have overnight guests a few times a year. Does it make sense to close off those rooms when they aren't in use? If so, should I seal off the return vents as well as the supply vents?
Also, in a recent column you mentioned that adding insulation might be a cause of moisture problems. I'm considering upgrading my attic insulation from R-30 to R-49 by having insulation blown in. Is there any way to determine in advance if this might cause moisture problems? Are there particular steps I can take in advance to avert moisture problems?
A: I'd close the supply vents for sure, but I'm not all that sure about the returns. You might want to give the furnace servicer provider a call to determine whether doing so will affect the efficiency of the unit.
As far as moisture and upgraded insulation are concerned, I'd just keep an eye on things. If you have bathrooms, the dryer, the cooktop, and other sources of indoor moisture properly vented, you shouldn't have a problem.
How do you determine if you have moisture problems in your attic? Moisture will manifest itself as darkened stains on wood surfaces, typically starting at the joints. Damage to insulation is often difficult to identify without feeling the material for moisture. You should also look for mildew or mold that can accumulate on some insulation materials and attic wood and wallboard surfaces.
Want Alan J. Heavens' advice on a home-improvement project or purchase? E-mail him at email@example.com or write to him at The Inquirer, Box 8263, Philadelphia 19101.