Thermal Comfort in the Home

There is a common saying, especially to those who grew up in areas such as Southern Ontario and Nova Scotia that says “it’s not the heat, it’s the #%$@# humidity!”. We in the Halifax area feel the effects of our humid summers and even though we live in a cold climate, it certainly doesn’t feel that way in the dog days of summer! 
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In short, it’s not just about what the air temperature is that determines our comfort level. Having a background in building services, I have done extensive training in the complex nature of modern buildings and how measurables such as temperature, humidity and pressure are continuously monitored and fine tuned. This is known in the industry as psychrometrics. To give you a quick idea of how complex these calculations are, here is a simple psychrometric chart.

Don't worry, there won't be a test!

I would imagine that your eyes glazed over at this point. This blog is written for you, the everyday homeowner and not an HVAC specialist so let’s break it down in simple terms: the comfort level in your home is based on both temperature AND humidity, which are heavily influenced by air pressure. 

Understanding Air Pressure in One Minute
Something few homeowners consider is the importance of balancing air pressure in a home. Put simply, air always flows from higher to lower pressure. Having a positive pressure relative to the outside will cause air to be pushed into walls and insulation and having negative pressure relative to the outside will cause outside air to rush in to balance out the pressure difference, neither of which is desirable, especially on a cold winter day. This can also lead to a common complaint I hear about woodstoves and fireplaces causing smoke to enter the home rather than go out the chimney. Like in most homes, our air vents were strategically placed to maximize air balancing and keep conditioned air inside the home where it belongs, while minimizing heating and cooling bills. 
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Humidity is Important Too!
It is important to consider not only temperature but relative humidity as well. A general rule of thumb is that it should be between 40-60% in the average home. Since cold air holds a lot less moisture, heated winter air can be very dry. This can lead to many issues such as bloody noses, dry skin, asthma, static shocks and cracked wood products. 

We are in the time of year where the average home can start to have too much humidity. Not only can this lead to feeling hot and uncomfortable, but also mold growth and moisture damage to the home. As I have said countless times, moisture is the #1 enemy of homes. Therefore, it is imperative that homeowners operate a dehumidifier in the summer months. If this post doesn't make it clear, there are many very good reasons to have your HVAC system inspected annually by a qualified technician.  

The low humidity indicates this picture was probably taken on a colder day.