Ducts need cleaning

Q.  I own a home with electric air conditioning and forced-air heat. I have owned the home for five years. I have three dogs: two collies and a Boston terrier.

I have not yet had the air ducts cleaned. I wonder if this is something that you recommend be performed on a regular basis. If so, how often? Also, can you recommend a qualified company to perform this work or advise as to how one would best go about finding one in their area?

A.  Yes, you should have the ducts cleaned. They collect a lot of dust — and dog hair — that can breed unpleasant bacteria and odors. You can find companies that do this type of work with an Internet search or your Yellow Pages under “Duct Cleaning”.

Insulating AC ducts to prevent heat loss

Q.  We have hot-water heat and separate air conditioning with ductwork in the attic. I have never seen anything published regarding heat loss through the vents for the air conditioning in each room. There are no levers for shutting off  the vents. Should there be?

A.  The air-conditioning ducts in the attic should be insulated. There are several types of ducts. If they are flexible, round fiberglass ducts, they come insulated. But if they are metal, they are insulated with special blankets with an aluminum facing. The air-handler is also insulated.

But since the system is in a cold space and the registers on the ceilings, warm air will enter the registers, and since the R-factor of the insulation on the various parts of the system is nowhere as high as it is in the other components of the house, there will be some heat loss.

The ceiling registers  should have some sort of adjustment to close them partially or fully, in order to balance the system. Since yours do not, you may want to look for replacements.

Loud creaking noise when furnace blower comes on

Q.  I own a 28-year-old split level in New Jersey that has forced hot air heat (natural gas) and central A/C. For the last several heating seasons, when the furnace blower turns on to circulate the warm air, there is a horrible (and getting louder) creaking noise coming from a register.

I think it is because the supply runs, which are all metal, expand and the creaking begins. After a few minutes, when the supply ducts get warm, the creaking stops. It does not creak when the ducts cool off. It seems to happen when the heat turns on after a setback period which is about 30 minutes before I get out of bed!

The noise is in a duct that is in the ceiling above my family room that heats an upstairs bedroom. Is there any way short of ripping down the ceiling to secure the duct and keep the noise from happening?

A.    The creaking may be due to the offending supply duct being restrained by a fastener or oil-canning as it heats. You may want to call a warm-air heating contractor to investigate and offer a solution. You may not need to cut the ceiling open if the restraint is close to the register.

Heat lost in complex network of ducts

Q.  We purchased our home 16 months ago and realized last winter that the heat in the master bedroom is insufficient. The room was added to the dwelling by the previous owner three years ago and was heated/cooled via a flexy ductwork tube, which began in the basement, snaked up the side of the house then branched into four separate flexy ducts in the attic, entering our room through four vents in the ceiling (whew!).

I have been told by my HVAC technician that this is too far for the air to travel efficiently (by the time the air came through the vents, it was cold). We have since disconnected this contraption and have boosted circulation to other rooms in our home (air was being leeched-off the main duct for the master bedroom). But we are now left with a very chilly bedroom.

My question: Do we abandon all of the ductwork above the ceiling and install baseboard heat? Or do we look into a heat-pump system, which I understand is a bit expensive? The room stays comfortable in the summer, so we have gotten by without a window unit. Heat appears to be the biggest obstacle.

A.  You are right! Whew! Who ever thought this system up? The air running through a duct or ducts from the basement to the bedroom on the outside is bound to become cold by the time it reaches its destination.

Ask your HVAC contractor for his or her advice on the most practical way to increase the heat in the bedroom. A separate through-the-wall unit or even electric baseboard  may turn out to be the best solution if the present system cannot be satisfactorily extended within the conditioned envelope of the house.

If you have gas, you may want to consider having your HVAC people install a through-the-wall Rinnai heater. These heaters are very efficient and can easily be sized to fit the need of your master bedroom.

Ductwork sweats and drips

Q.    The warm-air furnace with air conditioning is in our basement. In the summer, there is a severe and intolerable damp mildew smell in the basement. The ductwork closest to the unit sweats and drips onto the floor and we believe that this is the origin of the odor. Is there a way to remedy this smelly problem? We have bought a top-of-the line dehumidifier but it has not taken care of the problem.

A.    A dehumidifier would be the solution I would suggest but since you have one and it does not take care of the problem, you should have the plenum on top of the furnace and all accessible supply ducts in the basement insulated.

Obviously, your condenser is fully-charged and operating efficiently, thus sending very cold air through the plenum and the supply ducts. Insulating these ducts would push the problem further down the line but the inaccessible supply ducts to the first floor registers are very short.

Those to the second floor (if your house has one) have such a small cross section that the cold air going through them would cool the surrounding area enough to prevent the dew point and condensation.

Connecting a pellet stove to existing ductwork

Q. Our house has an older model forced-air oil furnace and a new hot-water boiler oil furnace. With the rising cost of oil we would like to have a pellet stove installed using the duct work from the old forced air furnace. Is it possible? We don’t want to purchase a pellet stove and not be able to use it. We are mainly wanting the pellet stove as backup.

A. I see no reason why you can’t install a pellet stove in lieu of your old furnace, but I suggest that you contact a stove dealer who handles pellet stoves and have him or her come to your house to make sure it can be connected to the existing ductwork.