Restoration Guide: HVAC Controls

Jeffrey Anderson


Editor's Note: This is article 8 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.


One of the easiest and least expensive ways to contribute to the energy efficiency of your old house is to update the controls used to regulate your heating and air-conditioning system. Section 8--HVAC/Plumbing volume--of Old House Web's Restoration Guide takes a look at what modern HVAC controls are available and what benefits they can provide.

Section 1--Overview

It wasn't that long ago that controlling your heating system meant lighting or putting out the fire in a fireplace. That is not longer an issue with today's HVAC controls. From adjustable electronic thermostats to outdoor sensors, humidistats to force-air zones, HVAC controls provide homeowners with complete control over the temperature regulation and energy use of their homes.

The function of a thermostat is to sense the room temperature and adjust the temperature based on your settings. The best location for a thermostat is about five feet above floor level, and away from any heat sources such as supply registers or direct sunlight. The technology used in thermostats has advanced substantially during the past decade, so during your older home restoration it might be a good idea to replace your controls if they appear to be older than that.

Section 2--Installing an Electronic Programmable Thermostat While Remodeling

Just like a lot of household products, as a thermostat gets older it may not function as well as it did when new. Older electromechanical thermostats can lose calibration and interior parts can wear out. It is possible to clean and re-calibrate older thermostats, but with all of the energy saving advances available with new HVAC controls, it might be money well spent to invest in a newer, programmable electronic thermostat.

Electronic thermostats are traditionally more efficient and respond more quickly than electromechanical thermostats. Today's electronic thermostats allow homeowners to set different temperatures for different parts of the day, and some even allow for different settings for different days. This type of temperature control could help your save money on energy costs as you can program your thermostat to lower the temperature at night and while you're away from your home.

More advanced electronic thermostats can even adjust the temperature based on light levels in the room and whether the room is occupied. Some models even come as remote control devices, allowing you to control the temperature from any room in the house.

2.1: Add a Humidistat to Your HVAC System

Depending on the climate in their area, many homeowners add a humidifier to their HVAC system during their home renovation. If your home is located in a warm, humid climate, you might want the ability to control the humidity within your home as well as the temperature. Installing a humidistat provides you with the ability to create a humidity setpoint, which the humidistat regulates throughout the day using your air conditioner or humidifier.

2.2: Add a Control System with Outdoor Sensors

Sophisticated HVAC system controls have temperature sensors which can adjust your heating and cooling system based on outside conditions as well as the interior temperature of your home. If you installed a heat pump system during your house restoration, and it has supplemental resistance heat, the temperature it comes on can be adjusted with input from an outdoor sensor system.

2.3: Add Ventilation Controls to Your System

As discussed in a previous section, interior ventilation is important to maintain air quality in your old house. If you added a ventilation system during your remodeling, controls can help it work properly. Ventilation controls can be simple such as an on and off switch, or you can install more advanced controls such as a timers and speed controls that can turn off your fan at a certain time or allow you to choose the rate of air flow in the house.

Automatic controls are available as well and include programmable time clocks that can determine when ventilation or fresh air is needed.

2.4: Add Forced-Air Zone Controls to Your HVAC System

Many old houses have a two zone HVAC system which allows you to adjust the temperature in each zone. If you have a one zone system, but would still like the ability to adjust the temperature in individual areas of your home, a forced-air zoning system might be the answer. The system allows you to use several thermostats which control motorized dampers within the distribution system. This gives you the ability to reduce the amount of heat or cooling going to unused portions of your home. This type of system should be installed while you are remodeling your HVAC system, but it is possible to retrofit after renovation.

The forced-air zone control system requires careful design, as care must be taken that even if several zones are reduced or closed, the system still has minimum air flow to operate properly.


About the Author

Jeffrey Anderson has a Degree in English from V.M.I. and served as an officer in the Marine Corps. He worked in Residential and Commercial construction management for 25 years before retiring to write full time.

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