Heat recovery ventilators (HRV) can help prevent your home from losing heat. They can also help with airflow, eliminating stale or stagnant air. Modern homes are well insulated and much more efficient than older homes. Prairie winters, like those in southern Alberta, can be very cold, making heat loss a serious problem. Though modern insulation is great for keeping the heat in, it can also trap humidity, which isn’t always ideal.
The Problem with Warm & Stale Air
Warm air tends to absorb increased humidity. Every time you use the shower, dishwasher, dryer, or washing machine, you raise the humidity level in your house. Unfortunately, when we vent humidity, it tends to take the heat with it.
Heating your home is expensive, which means that venting humid air can also cause your heating bill to rise. Failing to remove excess humidity from your home can have serious consequences in the long term, including mould and mildew forming in the walls and inner structure of the home.
A heat recovery ventilator (HRV) can help with both heat loss and air circulation. HRVs work first by circulating air indoors and then getting a flow of the air from indoors into a ventilator. The ventilator also has a cold air intake so it can mix these types of air.
The key to keeping your home both warm and dry is exchanging the heat between cold fresh air and hot and stale (humid) air, which can be accomplished by mixing the air with the help of a heat exchange. Aside from a heat exchange itself, your HRV will also need a fan to move heat-recovered air into the home. Putting another fan on the stale air intake can increase heat recovery further.
Common Types of Heat Recovery Ventilators
There are a few common types of heat exchangers for heat recovery ventilators, each with their own strengths, weaknesses, and associated costs. To help you better narrow down your choices, we’ve compiled a list of common types of heat recovery ventilators below. However, before you make your final decision, you should consult with an experienced HVAC professional.
Rotary Thermal Wheel
A rotary wheel uses circular motion to transfer heat from the stale air stream to the fresh air stream, allowing the cold intake air to collect heat off of a continually turning wheel, and return that heat to the home as warm air output.
Fixed Plate Heat Exchange
This style of heat recovery ventilator is the most common, and with an average success rate of 90%, it is often the most efficient. Multiple fixed plates collect heat as stale air flows through them and dissipate the heat into the fresh air that is being drawn into the home.
A heat pipe uses an evaporator and a condenser to take advantage of water changing from a liquid to a vapour and back again to cool stale exhaust air while warming fresh intake air.
A run-around leverages two heat exchange types in a combined system. They use gravity to drag air down from one heat exchange type (typically a fixed plate exchange) to a second, different style of heat exchanger (typically a heat pipe style exchange).
Phase Change Materials
Phase change materials (PCM) are a newer style of heat exchanger and don’t actually require a ventilator. They are typically built directly into the walls of newer houses and use beads that melt and solidify as the temperature changes to regulate the home’s internal temperature When the walls are warm in the summer, they have a cooling effect. When the walls are cool in the winter, they produce a heating effect.
The Difference Between ERV & HRV
An ERV (Energy Recovery Ventilator) works in much the same way as an HRV, since it uses the same types of heat exchangers like fixed plate heat exchangers and rotary thermal wheels. The big difference is that ERVs remove heat from air-conditioned air so that the house stays cool.
An HRV will give your home the efficiency of giving your furnace a break and can improve your home’s air quality. While not all homes have air conditioners, almost every Canadian home has a furnace and could benefit from an HRV. Whatever style you go with, an HRV can help increase your furnace’s efficiency and lower your heating bill.
Though they can represent a hefty up-front cost, adding an HRV can help reduce your heating bill, saving you money and paying for itself in the long run. HRVs offer the most bang for their buck in places like southern Alberta, where seasonal temperatures vary widely.
Can an HRV Save Me Money?
HRVs can help your home retain heat without getting stale or musty, saving you money and increasing your home’s air quality and removing excess humidity from your home. By removing excess humidity, you could save yourself costly repairs related to moisture from the air in your home seeping into the surrounding structure.
Avoid Stale Air Buildup by Installing an HRV
Stale and humid air can cause a few problems. It can cause mould and mildew to grow in your flooring, walls, and ceiling, and left unchecked may negatively impact your health. Excessively stale or moist air may increase your chances of developing asthma and can encourage the growth of dust mites.
Given how effective HRVs are at keeping humidity down, and how they can lower heating costs for homes running a furnace day and night during cold Calgary winters, an HRV is a worthwhile investment, especially for newer homes.