HVAC Meaning
The term HVAC can be confusing for a lot of home buyers. In the context of a home inspection, we are talking about Heating, Ventilation and Air Conditioning. In newer homes, it is common to see all 3 form an integrated system.
High Efficiency, Two Stage, Modulating, & Zoned Furnaces
Let’s start with heating. Most new residential homes have a high efficiency forced air system. Multiple heat exchangers, two PVC pipes – one for intake, one for combustion air and a blower fan. You might hear the term “two speed” or “two stage furnace”. The best way of explaining this is to imagine driving through downtown Edmonton by flooring it if you want to go forward. How much gas would you be able to save going half the speed? A two stage furnace meets normal energy demands, usually at 66% of the furnace capacity. During a cold snap, our lovely -30C nights, the furnace goes at 100% capacity. Modulating furnaces have all kinds of controls for the exact amount of fuel and heat distribution. These systems can get complicated and more things can go wrong. You can also expect repairs to be more expensive. You can also have zoned furnaces that have different temperature settings for different areas. Let’s say you have a two-story house with all the bedrooms upstairs. The main floor can be set to 15C at night with the upstairs set to 17C at night. Over time, this will contribute to energy and cost savings.
Heat Recovery and Energy Recovery Systems
If we ever want to achieve net zero house, an HRV/ERV is an absolute requirement. In the winter, this is taking cold, dry intake air and mixing it with warm, moist exhaust air. Basically, preheating our combustion air and reducing the heating requirement. There are great drawings on the units themselves showing what is happening. The filters in these can get filthy!
Air Conditioners
There are 2 seasons in Edmonton, this winter and last winter. But air conditioners are becoming normal, several types are on the market, the most common is a single package vertical air conditioner. This is usually tied into the same duct work as the furnace and becomes a full HVAC system. Window mounted units can be found for pretty cheap, especially used. Fair warning! These very inefficient and are best for cooling down one room. Check your AC unit every year and have it the cooling fins cleared of dust, otherwise the efficiency will be reduced.
Emerging Technology
Heat pumps are an emerging technology, marketed as being over 100% efficient… This is not true, it is thermodynamically impossible. BUT an air source heat pump can produce 2kW of energy for 1kW of input, giving a coefficient of performance, COP, of 2. We aren’t making energy, only moving it from one place to another. Heat pumps and AC units can grow mold and it my experience, it is usually black. The 4 seasons we see in Edmonton: early winter, winter, late winter and next winter cause reliability issues for conventional heat pumps. There are “high heat” versions which may become popular in the future, but the last thing anyone wants for the heating to fail during a January night.
Don’t Forget
It is imperative to change and clean all the relevant filters in your HVAC system. Give yourself an annual reminder, or better yet, subscribe to our home maintenance newsletter. You should be changing your furnace filter as directed by the manufacturer, minimum annually. The HRV/ERV filters can be completely clogged with bugs, dust and debris. Also, if there is a humidifier, that should be checked. Your HVAC efficiency will be reduced and will probably reduce the life of the system.