Restoration Guide: HVAC Design and Engineering

Editor's Note: This is article 2 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.

2. HVAC DESIGN And ENGINEERING CONSIDERATIONS FOR OLD HOUSE RESTORATIONS

A properly operating HVAC system contributes to the overall comfort of an old house's occupants, and the efficiency of the system, along with the type of fuel it uses, can have a considerable effect on the cost of living in an older home restoration. In Section 2 of Old House Web's edited version of the HUD Rehab Guide's HVAC/Plumbing volume, using an old house's existing HVAC system or replacing it with a modern system during the home renovation is discussed.

Section 1--HVAC Design Overview

Much has changed in the world of residential heating and cooling over the last hundred years. Older homes often had inefficient heating systems, and cooling was handled by the use of ceiling fans and opened windows. The HVAC design and engineering of today can produce high interior comfort levels with lowered energy usage, and provide the cost savings that accompanies the reduced use of operating fuels.

When undertaking an older home restoration, the existing heating system should be inspected, and a decision made as to whether it should be replaced. The existing heating system being operable, or having the ability to become operable, is just one of the factors that should be considered when making the decision on using the system or replacing it. Other factors that should be taken into account are:

• The efficiency of the system
• Cost of the fuel used by the system
• Interior comfort level the system can provide
• Cost to replace the existing system

In many cases a particular fuel was not available when the old house was built, but is now available, and can provide a less expensive means of heating the home. The cost of replacing an existing system while remodeling your old house is usually offset by the long term energy savings and increased comfort level a modern system can provide.

Section 2--Sizing a New System for Your Older Home Restoration

If the existing HVAC system in your old house can not be repaired, or you have decided to replace it with a more modern system, the size of the new system should be considered. Old houses often had large heating systems to help compensate for poor insulation practices, and air infiltration through and around windows and doors.

Older home restoration often involves adding insulation, and installing energy saving windows and doors. If you are planning an extensive home renovation, and not just replacing the HVAC system, you may be able to use a much smaller unit than what was originally installed. HVAC contractors can be helpful in sizing a new system, but you may want to consider consulting with a mechanical engineer. A mechanical engineer is not trying to sell a particular piece of equipment, and they can also make a determination as to how changing the HVAC system might affect the other systems in the home. Depending on the size of your old house, and the budget you have allocated for remodeling, you may want to use a mechanical engineer for your HVAC design and engineering.

Section 3--Energy Sources for Your Old House

Old houses often used wood, coal, or oil as an energy source, and depending on availability, price, and the climate of your area, you may decide to continue with the original energy source. The most common energy source used today for heating is natural gas, and electric is the most used energy for cooling. Some of the energy sources used today are:

1. Electricity. This is one of the more expensive fuels, and if you live in an area which experiences cold winters, you may want to consider another type of fuel for heating. However, if you live in a moderate climate, electricity is a clean fuel, and has the convenience of being able to be used for both heating and cooling.
2. Natural Gas. This is one of the least expensive heating fuels, and is popular due to its being a clean fuel and not requiring a storage tank. Natural gas is not available in all areas.
3. Oil. This is a popular heating fuel in areas which experience cold winters and in which natural gas is not available. Prices can fluctuate, and availability may diminish in the future. Oil requires a storage tank.
4. Propane. Propane is often used when natural gas is not available, and the area gets cold enough that electricity is not a viable option. Propane is delivered in trucks, and requires the use of a storage tank.
5. Solar. Solar heat as an energy source is gaining popularity with the recognition that other energy sources may become costly or in limited supply. Passive solar systems involve the use of building materials and the orientation of the home to take advantage of the sun's heat. Active solar systems use pumps and fans to help distribute collected heat.