Wildly varying bids for heating units is concerning

Q. Would you be willing to give your opinion on the two oil furnaces proposed for our home? Airco's is 120,000 BTU, 84.4-percent efficiency, not a variable motor (or two-state blower), vent to outside vs. chimney; Bryant's is 82,000 BTU, 85-percent efficiency, variable-speed motor, vent to outside vs. chimney.

Our home is approximately 2,000 square feet, with only one thermostat for the entire house. We have been heating with a coal furnace, which gave us even heat. My biggest complaint is the new oil-fired furnaces will not provide even heat; it will get cool in the house before it comes back on. I will miss that about the coal furnace.

A. My concern about the two bids you received is the huge disparity between the two in BTUs.

Employing an oversized furnace or boiler is not only bad for the environment, but it will also shorten the life of the heating appliance and affect your comfort negatively, as you so clearly realize. Using an undersized heating appliance may cause it not to be able to keep you comfortable even in moderate temperatures.

Coal, pellet and wood as fuels do provide a wonderfully even heat, but coal and wood require frequent tending, which can be burdensome.

An oil-fired furnace or boiler, if properly sized, can provide even heat in the average regional cold temperatures by running constantly, as it should.

In unusually cold snaps, it may not be able to satisfy the thermostat's setting, but wearing a sweater can easily take care of the slight deficiency for the duration.

The fan can also be set in the CAC (constant air circulation) mode to keep the air circulating throughout the house.

While an oversized furnace will keep the house at the thermostat's setting regardless of how cold it gets, there are several negative aspects to it. When the furnace fires up, it may create uneven heat in some areas that become too hot before the thermostat shuts the furnace off. Then the furnace may take some time to fire up again, allowing the temperature in the house to drop significantly, affecting the comfort of the occupants. This is a particular problem for less energy-efficient houses that are prone to greater temperature fluctuations.

A furnace that cycles on and off frequently spends much of its time reaching the air temperature needed to bring the house to a comfortable level - a waste of time and energy.

Another deleterious effect of frequently cycling on and off is that it wears the equipment faster, reducing its life. A warm air furnace has a heat exchanger, which expands as it is heated and contracts as it cools between cycles. Metal fatigue can shorten the exchanger's life significantly, and if not detected, can lead to the introduction of carbon monoxide into the living spaces - a potentially deadly situation.

For an existing house, the HVAC contractor should run a heat loss analysis of the entire house to determine the correct sizing of the heating appliance.

So I am very concerned that one of the two contractors who gave you bids is way off, one way or the other. I'd advise you to ask some questions:

• Have you run a heat loss analysis of our house? What is that heat loss, and how did you reach the decision to size the furnace in your proposal?

• Is the furnace you are suggesting oversized because you want to make sure we have enough heat for even the coldest cold snaps? Or are you sure that the furnace you propose is not undersized, which would not keep us comfortable most of the time?

It is important to know that the same applies to boilers in hydronic systems. Warm air systems do not usually come with different zones. If that is what you want, two or more zones can be engineered by using motorized dampers, but it is an expensive system and one prone to repeated maintenance.

Heat output in different rooms can be regulated by adjusting the rooms' supply registers. It is important to have high-quality supply registers, which provide directional distribution on all four sides, if they are in the ceilings, or on three sides if they are at the base of walls. They are more expensive than run-of-the-mill supply registers, but well worth the added cost.

Venting to outside through a wall or band joist is common nowadays. Venting through existing chimneys is not the best way to vent furnaces or boilers because the exhaust gases are cooler than those in inefficient heating appliances and can cause chimney problems, such as condensation, which can loosen up old oil residue that may run down the chimney and cause unwelcome consequences.

Q. I am planning to re-tile my bathroom, including the bathtub area, with ceramic tile (probably subway tile) over sound 4¼-square-inch ceramic tile. (I don't want the mess of a complete tear-out.) I have a few questions for you:

• What type of bonding should I use - mastic or thin set, and which brand would you suggest?

• After roughing the surface, I am thinking about drilling quarter-inch holes (with a masonry bit) in the grout of each corner where the tiles meet to give the new tile a bit more bonding. Is this a good idea, will it help or is it not worth the bother?

• What type of grout should I use?

• Is there anything else I should know or do?

A. That's an ambitious project, but it can be done. The process depends on the type of existing tiles. To determine this, you should have an experienced tile contractor or tile store associate look at them.

The existing tiles will have to be thoroughly cleaned to remove any soap scum and other pollutants. If they have a hard, shiny finish, they will either need to be etched (the method to use will also depend on the type of tile), scoured lightly to prepare them for the bonding agent, or primed with a special primer that is compatible with the thinset you will need to use. A tile store associate or experienced tile contractor can also advise you on the proper preparation.

You will also need to make sure bullnose caps are available for the tiles you propose to apply over the existing tiles, or you will have a problem at the top and ends.

Another problem may be how to handle the base of the walls. It is likely that the bases of the walls have tiles forming a cove. If you want to use cove tiles, they will stick out a quarter-inch over the existing floor. If you choose not to use cove tiles, how will you take care of the space between the floor and the bottom of the new tiles?

And how will you handle the bottom of the tiles over the tub? The tiles are likely to protrude over the tub's curved edge.

If you feel comfortable about solving all these issues, once the existing tiles are ready for the subway tiles you choose, Thinset 254 is the adhesive to use.

Drilling holes in the grout should not be necessary, and can actually cause problems since the subway tiles are not likely to match the pattern of the existing tiles.

The tile store can also advise you on the type of grout to use; epoxy might be a good choice.

Q. I have installed a new concrete driveway with a drain and sump pump well in the driveway. The well is 30 inches deep. I wonder if I need to remove the pump during the winter months or if it can be left connected in case of melting snow or rain. The installation was necessary due to elevation changes from the road edge to the garage floor height.

A. You should remove the pump for the duration of the winter, and take your chances on rain and snow melting. I don't think that a 30-inch depth in the open is deep enough to protect the pump from freezing. Your area does have some pretty severe weather.

You can install a quick-connect feature so it is easy to remove and reinstall the pump to the discharge hose, if need be, to empty a filling sump.

Interesting comment from readers: In response to an earlier question from a reader about a mysterious sewer smell in a bathroom that persisted in spite of the replacement of the wax seal:

"I had the same problem with a sewer odor in my bathroom. The culprit turned out to be a nail that went through the vent pipe. Somehow, during construction, a carpenter nailed something and the nail went into a vent pipe and chipped a small hole in it. The hole was actually in the floor above the bathroom, but it sure smelled like it was coming from the toilet area. Once the plumber fixed the broken vent, all was solved. We were lucky that the broken pipe was in an unfinished attic area. Not sure how it would be found in a finished area. In our case, the break was quite a ways from the odor.

"I wonder how a carpenter drove a nail in the vent pipe in the attic!"

And another one on the subject of a mysterious sewer line clogging, which a plumber's snake cleared, but for which no reason was found:

"I felt you covered most of the possible solutions for the homeowner, but maybe it would also help to suggest bringing in a plumber who uses a camera that they insert in the pipe, since nothing was found with the snake. I lean toward not enough fall in the pipe also."

• Henri de Marne was a remodeling contractor in Washington, D.C., for many years, and is now a consultant. His book, "About the House," is available at www.upperaccess.com. His website is www.henridemarne.com. Email questions to henridemarne@gmavt.net, or mail First Aid for the Ailing House, Universal Uclick, 1130 Walnut St., Kansas City, MO 64106.

© 2015, United Feature Syndicate Inc.