Hot water boilers make a comeback; In recent years, technical upgrades made for gas, oil boilers

Q: I am adding two rooms to my house for my parent's apartment. Ihave heard boilers make comfortable heat, especially for theelderly. Are they efficient? Can I also use one for the rest of myhouse?

A: Hot water heat was very popular years ago. It went out offavor somewhat when central air-conditioning became commonplace.Since central air-conditioning required a duct system, forced-airfurnaces were usually installed.

Today, with the high cost of heating homes, hot water boilers arebecoming more common again in all climates. This is partly becauseof the comfort and efficiency of a hot water system. Recenttechnology improvements in gas and oil boilers have made theequipment as efficient as forced-air systems.

For cooling during the summer, there are several central air-conditioning alternatives to a standard ducted forced-air system.

The most common are minisplit ductless systems and miniduct, high-velocity systems. The miniduct system can also be used for heatingyour home.

Boilers are available in many sizes (heat output capacities), soyou should be able to find one small enough to efficiently heat justtwo rooms. Most of the residential models are also available up to200,000 Btu heat output, which is enough to heat a very large housein the coldest climates.

As with gas and oil forced-air furnaces, you can get a $150federal tax credit if the efficiency (AFUE) of the boiler is 95percent or above. In order to meet this requirement, many of the gasboiler manufacturers have slightly modified their designs to meet orexceed this requirement.

There are only a few oil boilers that also are in the 90-plusefficiency range. For the highest efficiency that qualifies for thetax credit, a boiler uses a condensing heat exchanger. Thiscondenses the water out of the flue gases to squeeze out more heatbefore they are exhausted outdoors.

A condensing boiler design is ideal for your room additionbecause it does not require a chimney. The flue gases are exhaustedthrough a small plastic pipe.

These high-efficiency boilers use a low-mass heat exchanger,usually made of stainless steel. A few use specially coatedaluminum. Low-mass heat exchangers heat and cool quickly so thesystem can adapt quickly to changing heating needs of your house.Non-condensing models often use high-mass cast-iron heat exchangers.They are less efficient, but very durable.

The typical heat delivery options are baseboard radiators, in-floor radiant tubing and/or a heat exchanger with a blower. Sinceyour parents are older, in-floor heating would be an efficient,comfortable choice.

The room temperature reacts slower to thermostat changes, butyour parents might not tolerate a nighttime setback well anyway.

Update Bulletin No. 490 is a buyer's guide of 15 efficient gasand oil boiler manufacturers, listing 29 models, efficiencies,sizes, venting methods, warranties, features and a savings/paybackchart. Please send $3 and a business-size, self-addressed, stampedenvelope to: James Dulley, Chicago Sun-Times, 6906 Royalgreen Drive,Cincinnati, Ohio 45244, or download from www.dulley.com.

Q: My house has brick veneer over insulated stud walls. I amgoing to build a raised deck off the second-floor bedroom. It willbe supported by four posts. Should I attach the deck floor to thehouse wall?

A: It is probably better if you do not attach it securely to thehouse wall. With tall wooden posts, the deck surface might move upand down more than the house wall throughout the seasons. This canstress the materials.

To provide a more stable feel to the tall deck, screw steelangles to the house wall. Screw another set of angles to the deckseveral inches below the other ones. Connect them with long boltsthat allow some vertical movement.

James Dulley is an engineer.