This article was written by Halco owner, Hal Smith, and published in ACCA's newsletter, IE3. Please click here to visit the original publication.
When choosing the right size heating and cooling system for your customer, it would be a great practice to give them the choice to round down. Traditionally we have all been taught to round up and that bigger is better!
When it comes to a healthier, more comfortable home, in my opinion, this is no longer the best way to do things. When you consider the whole house as a system and all the pros and cons of rounding down, at a minimum it makes sense to educate your customer and give them a choice. Bigger is not better.
It is not about saving money or making the system less expensive, it’s about making the home operate better! Let’s be honest, how much money is involved when you’re going up or down a size in HVAC equipment? Peanuts! What I am talking about is better comfort, humidity control and air filtration for the next 20 plus years of operation of the equipment. This results in a healthy, efficient home.
Make Building Science Your Friend
When you use a blower door and a thermal imaging camera as part of your heat loss and heat gain calculations, you start to get very comfortable rounding down. Halco always calculates the BAS or MVG as well. It gives you a real gauge on where the house is and where it can be if you include some insulation and air sealing measures as part of your HVAC replacement package. It allows you to make very educated choices.
It’s Not That Scary
What is the worst thing that can happen when you round down after taking these measurements? Most likely, the fudge factor in the calculation will take care of most of it. But suppose it doesn’t…Let’s talk about that very cold overnight temp. Your heating system falls a little short and you can only get the house to 68 degrees instead of 70. Plug in a space heater and you have the difference! This is a very small percentage of the time. The rest of the time you get longer run cycles, which brings better temperature control, better comfort, more even and less drafty heat, all at a better operating efficiency. A lot of benefits for a small amount of trade off.
Two stage furnaces as well as modulating furnaces have contributed a great deal towards these same benefits, but even these furnaces work better when sized closely and, most times, rounded down.
The benefits on the air conditioning side of things can be even more plentiful. Humidity control in homes today plays such an important role in the overall health and comfort of the home. We all know that if a central A/C system never shuts off during the hottest day of the year, but still maintains temperature, it would be perfectly sized.
Insulate and Seal the Ductwork
Pay close attention to ductwork that is outside the pressure and thermal boundary of the home. Make sure that this is well sealed and insulated as part of your proposal.
More About Making Healthier Homes
In our work of retrofitting old homes, we find controlling humidity to be a big challenge. We must control moisture as we tighten up the home. In our market, we have a lot of dirt crawl spaces and basements.
We have recently added basement waterproofing to the list of services we provide. We find it very beneficial when we think of healthy homes.
Years ago, we use to install thousands of humidifiers. We almost never install humidifiers anymore after tightening up an old home. Typically, normal bathing and cooking provide ample humidity for a home that has been tightened up! The fact is that a central dehumidifier is sometimes needed year-round. When you keep the humidity level in the right range, you don’t grow mold along with many other benefits. Even consider a ventilating dehumidifier when you have a very tight home
Healthy homes are a very important piece of the market today. Rounding down and treating the home as a system can play a significant role in improving the health of a home. When you round down you have a much better chance of the ductwork being sufficient in size! Running the blower on a low, constant fan while filtering the air along with proper humidity control are all very important pieces of the puzzle that go hand in hand with HVAC equipment that is not oversized.
At the end of the day, round down! Bigger is not better! Smaller, properly sized systems, with decisions made from gathering more information, is a better approach!
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