By Nate Adams — The House Whisperer — Healthy Indoors Magazine January 2020 —
Done right, the HVAC in your home can make it very comfortable, and very healthy. One might even call it bad ass. But it needs to have a few relatively simple tweaks to be able to deliver what we call the 6 Functions of HVAC, and do it well:
- Load matching
- Fresh air
The trouble is 87% of heating and cooling systems are replaced on an emergency basis. This means mindfulness of the 6 functions is overridden by “I need heat ASAP, and as cheap as possible” myopic urgency.
If you have an HVAC system (furnace, air conditioner, heat pump, boiler, etc.) that is over 10 years old, it’s a good idea to build a replacement specification now, before you find a gun to your head and a hand rummaging through your wallet. Otherwise, when it dies, you’re going to get the first piece of equipment that the first guy who shows up wants to install, and it will almost certainly fail to make your home comfier or healthier.
Since these systems last 15-20 years, getting the equipment right avoids either replacing it twice (we have replaced very new equipment), or signing on to a long-term bad relationship.
When people hire us, we find the only consistent way to deliver better comfort through the 6 functions is to replace the system. Again, this is often replacing systems well before reasonable life expectancy. Think about how it feels to waste $8,000 – $20,000 replacing a system you recently replaced. It’s so wasteful!
We hate the waste, so we invented what we affectionately call BAD ASS HVAC. BAD ASS HVAC is a (pretty) simple system that can tackle the 6 Functions, and most HVAC contractors can install it.
Why are those 6 important? And what is BAD ASS HVAC? We’ll be exploring those over the next few months. Today we’ll talk about the first two – load matching and filtration.
We list the 6 functions in order of priority, and we’ve found load matching is the most critical for comfort.
Do you notice that your house is particularly cold on 40-55 degree days? Your HVAC is may be too large. If you graphed your temperature it would look like this, with air temperature going up and down quickly:
(From chapter 3 of the Home Comfort Book, page 101)
Furnaces and air conditioners are supposed to be sized to heat or cool on the coldest and hottest days of the year in your climate. At these temperatures the equipment should run continuously or near continuously. Calculating this “worst case load” takes some measuring and some math. The problem is without using a blower door to measure your home’s leakage, and looking at your energy bills, sizing your HVAC is a wild ass guess, with a broad variance of answers. For a LOT of reasons (fear, greed, urgency, ambivalence) people tend to lean way to the high side of the range.
Almost every furnace we’ve seen is at least twice as big as it needs to be.
So why does that matter?
About 60% of human comfort is based on radiant energy. Think about how pleasing a bonfire or sunny day is. Those are both radiant energies, and our bodies love it.
In our homes, radiant energy is given off (or sucked in) by the walls, floors, and ceilings around us. Right sized HVAC washes the walls, ceilings, and floors of your house with a slow steady stream of heat or cool. Nice even surface temperatures give off pleasing radiant energy just like a fire or the sun.
If you want to be comfy, we need to keep those surfaces within 2 degrees of the thermostat set point. To do that, we want our HVAC to be running almost constantly putting out exactly as much heating or cooling as our home needs at that moment – this is called “load matching”.
Read the full article in the January 2020 digital edition of Healthy Indoors Magazine at: https://hi.healthyindoors.com/i/1204626-hi-january-2020/41