Restoration Guide: HVAC -- Heating

Editor's Note: This is article 4 of 16 in Chapter 8: The HVAC/Plumbing Guide of Old House Web's Home Restoration Guide. This guide was developed and edited for old homes from original materials in the U.S. Housing and Urban Development (HUD) Rehab guide.

4. HEATING

Remodeling an old house often involves making a decision concerning the existing heating unit. Can it be used in its present condition, or has it reached the point where you should try to recondition it? If you are able to restore it, can it provide the efficiency, climate comfort, and cost savings that a new modern heating unit can provide?

Section 4 of the Old House Web's edited version of the HUD Rehab Guide HVAC/Plumbing volume takes a look at the existing heating units you may find in your old house, possibilities for making the existing unit more efficient, and what is available if you choose the replacement option.

Section 1--Heating Options for an Older Home Restoration

Depending on the age of your old house, and whether it has ever undergone any remodeling, there are various types of units that could be supplying heat for the home. Some old homes might have an oil or kerosene burning unit without a distribution system, providing a single source of heat for the entire home. If your old house is a little more modern, or has been remodeled, it probably has either a furnace or boiler. It might even have a more modern heating system such as a domestic hot water based system, supplying an air handling unit or radiant heat system.

One of the most common heating units found in old houses is the warm-air furnace. A warm-air furnace may be fueled by electricity, oil, or gas. If you happen to find an old oil or gas fueled furnace during your older home renovation, it may be well worth your while to replace it with a more modern unit. Gas and oil furnaces available today can operate at over 85 percent efficiency, as opposed to the 50 percent and 65 percent that was common 20 years ago. Due to the high cost of electricity, if you live in a cold climate, it might be cost effective to replace an electric fueled furnace with a gas unit.

When replacing a furnace during your older home renovation, take care to get the appropriate new unit. Furnaces are designed based on their placement in the house, upflow, downflow and horizontal flow units are available. This allows for placement in a crawl space or basement, an attic, or on a main level of the home.

In the early 1990s a small percentage of homes in the country used steam or water boilers as a heating unit, but almost 50 percent of the homes in the Northeast used them. While modern boilers are not as efficient as their furnace counterparts, the boiler heating system as a whole can be more efficient than a warm-air system due to the heat loss which can occur in the warm-air furnace distribution system.

Section 2--Renovation, Repair, and Installation of Heating Systems

The following are some suggestions for rehabbing and improving the efficiency of existing furnaces and boilers, and thoughts on installing new units. Any restoration or rehab work on an existing furnace or boiler should be done by a trained professional. Working with heating units can be dangerous without the proper training.

2.1: Installing a Flame Retention Burner on an Existing Oil-Fired Unit

A flame retention burner has a more concentrated flame and smaller air intakes, which improves combustion efficiency and allows it to burn hotter.

2.2: Add a Vent Damper to the Flue

The natural draft furnaces of today have standard vent dampers, but it was not always a feature in old houses. The damper closes when the burners are off, allowing the retention of heated air. This option can also improve efficiency if the furnace is located in a conditioned area, and relies on inside air for combustion.

2.3: Install an Electronic Spark Ignitor

Older gas fueled furnaces and boilers utilized a pilot flame that remained lit at all times, and constantly used a small amount of fuel. An electronic spark ignitor provides an ignition source that doesn't use gas.

2.4: Downsize the Burner Nozzle on Oil-Fired Furnaces

Old houses often had burner nozzles on oil-fired furnaces that were oversized to compensate for poor insulation practices, or just due to lack of design knowledge. It may be possible to downsize the nozzle and reduce the amount of fuel used. Downsizing a burner nozzle may require the fuel line filter to be cleaned or replaced more often.

2.5: Replace the Existing Heating Unit with a Modern High-Efficiency Gas Furnace

Budget is almost always a factor during an older home restoration, but sometimes money spent during the remodeling can provide savings in the long run. An older furnace, even with rehabbing, may never provide the efficiency and energy savings of an advanced modern unit. The most efficient modern gas furnaces can provide up to 97 percent efficiency, which can significantly lower energy costs. Some advanced furnaces even have multiple or variable speed motors. These furnaces can be expensive, and may require changing the size of the venting, but may be worth it if you are planning on living in your old house for a long period of time.

2.6: Replace the Existing Heating Unit with a Combination System

A combination system uses one heating unit for the home's hot water needs and for heating the home. A hot water coil runs from the hot water heater to the air handling unit or radiant heating system. This system eliminates the need for a furnace and its flue. A combination heating system requires a water heater designed for the system. These systems are still fairly new, and you may have some difficulty locating dealers who fully understand how to design them.

2.7: Replace the Existing Heating Unit with a High-Efficiency Boiler

New condensing boilers were not used very often during the preservation of old houses due to their inability to handle the high return water temperatures found in most hot water baseboard systems. However, there are now several manufacturers who have addressed this issue, and it is possible to install a new condensing boiler which can operate with the high water temperatures, and have an efficiency rating of up to 95 percent.