Simply Stated Architecture, P.C.

Preparing for Heating Season - Thermal Control

Today we’ll look at applying some lessons from commercial projects to your home to save on your heating costs.

With LEED (Leadership in Energy and Environmental Design) projects, commissioning is an integral part of the process. As a very basic explanation, commissioning is making sure that the mechanical processes of the building do what they were designed to do.

Understandably, tying everything together in a large commercial building is not an easy process. The HVAC (heating, ventilation, & air conditioning), plumbing, and electrical systems and their associated controls can be fairly complex. Whereas your home HVAC system typically has a single furnace and a single air conditioning unit supplying heat and cooling to the entire house, a commercial building may have hundreds of air handling units supplied by several boilers and chillers. LEED requires that certain energy efficiencies are met and the commissioning of the building is part of the guarantee that these standards are met. But even on non-LEED projects, commissioning can often be beneficial to make sure that these complex systems are operating in the manner in which they were intended.

There are quite a few things that can happen between the “paper” design and what is put together in the field. A favorite quote of mine, by Jan L.A. van de Snepscheut, is “In theory, there is no difference between theory and practice - In practice, there is.” What may seem to work on paper doesn’t always translate properly to the real world. Air currents affect thermostats, occupancy sensors may get hidden by other objects in a space, and placement of sensors in piping systems may be affected by flow and turbulence. So commissioning has been expanding beyond just LEED projects.

One of the steps in commissioning is air balancing. This is adjusting the HVAC systems to provide the proper amount of conditioning to spaces and this can be applied on a smaller scale in your own home. In my own case, I have a gas-fired furnace and central air conditioning system with registers in each room. Airflow is adjusted by manual dampers in the ducts in the basement and louvers at the registers in each room.

An example of a manual duct damper.
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The conditions and needs of certain rooms in my house change from season to season. My dining room and kitchen bear the brunt of the afternoon sun. In the summer, this means that they require extra air conditioning to maintain a comfortable temperature. In the winter, this means that they usually stay warmer too. Also, in the winter, I prefer to have my bedroom a bit warmer. So when I change over from summer cooling to winter heating, I make a few adjustments to the dampers and louvers. If I don’t make these changes, I’ve found that the greater airflow to the kitchen required for cooling in the summer leads to the kitchen being as much as 10 warmer than other parts of the house with the heat on. And that the bedroom is a bit cooler than I’d like for it to be.

It usually takes a few trips up and down the basement steps over the course of an afternoon for me to get things set right. I take a thermometer from room to room, first comparing it with the thermometer on the thermostat to make sure they are in sync. Then I will leave it in a room for ten to fifteen minutes to acclimate and start to adjust the damper accordingly to bring the temperature into line. In the springtime, I make similar adjustments when I switch over to air conditioning.

Another step in commissioning is the systems programming. Controls are set for HVAC, lighting, security, and a range of other systems within the building. On a smaller scale, a programmable thermostat for the HVAC system can help to regulate your energy usage. My thermostat allows seven day, twenty-four hour schedules. This means that during the heating season I can allow the house to cool off during times that I am regularly not at home or snugly tucked in under my covers at night. Similar schedules during the summer allow the house to be warmer when I’m not there. These have become very common in recent years and I’d recommend getting one if your house does not already have one.

A typical programable thermostat.
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As the most basic level, I’d recommend a 5/2 day programable thermostat that has the ability to schedule for weekday and weekend with four settings for weekdays and two for weekends. This allows for overnight, wake, leave (time you are at work or school), and evening settings during the week and then daytime and overnight settings for the weekend. Typical settings are to allow the house to cool overnight while you are sleeping and when you have left the house, warmer settings in the morning when you first wake and are dressing, and moderate settings in the evening hours. These have a manual switch to change from heating to cooling and allow you different schedules for each.

More complex thermostats can include occupancy sensors to adjust the settings based on whether there are actually people in the house, rather than just going by a programmed schedule. Also available are models with seven day schedules, the ability to be adjusted over the phone or internet, and “learning” models that adapt to different conditions automatically.

The control systems from commercial projects are also starting to make their way into home systems. Along with the programable thermostats, these systems include thermostats in each room or in various zones that control motorized dampers in the ductwork to adjust the flow of air to those areas. In my case, on a cold overcast winter day my kitchen does get a bit cooler without that afternoon sun to warm it. One of these systems would compensate for that and allow extra airflow without the need to run to the basement to adjust the dampers in such a situation. Costs for these systems are coming down and I expect to see more of them in homes in the coming years.

A motor controlled duct damper.
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