For the last decade or so, the trend has been to build tighter and tighter houses in an effort to reduce air and moisture infiltration. The idea here was to make homes more energy efficient. The problem, as everyone knows, is that sealing houses has resulted in poor ventilation. When a house can’t “breathe,” there is more of an opportunity for mold to grow, moisture can condense on windows, people may become sick more often, and a musty smell may be noticed.

The State of Minnesota recently responded to this issue by mandating mechanical ventilation in every new residential building. Its hope is that a constant flow of fresh air will alleviate many of the problems associated with tight houses. Meanwhile, ASHRAE Standard 62.2, while not final, is expected to require some form of mechanical ventilation in new homes.

Turning back to Minnesota, one of the options under that state’s new energy code is the heat recovery ventilator (HRV). According to the experts, HRVs are easy to select, size, and install, and the profit margin is “terrific.” So, the question remains, why aren’t more contractors offering them to customers?

The answer might be that contractors are afraid of new technology. Or perhaps they’re scared of making a mistake in the installation. But the fact is that many homeowners are looking for ways to make their homes more comfortable, and contractors owe it to their customers to offer a wide range of solutions — including HRVs.

How they work

HRVs are really very simple devices, as are their counterparts, energy recovery ventilators (ERVs). Both have a heat exchanger core, one or more fans to push air through the HRV unit, and controls. According to the Energy Efficiency and Renewable Energy Clearinghouse (a department of the Department of Energy), most models are capable of recovering about 70% to 80% of the energy in the exiting air and delivering that energy to the incoming air.

The way it works is that air from the living space is passed through the HRV unit and exhausted outside. Meanwhile, fresh air is brought in from the outside and also sent through the HRV. When the two air streams pass through the heat exchanger core, the heat from the indoor air is transferred to the fresh outside air. This results in a constant stream of fresh filtered air being delivered to the living space.

The main difference between an HRV and an ERV is the way the heat exchanger works. In an ERV, a certain amount of water vapor is transferred along with heat energy, while in the HRV only heat is transferred. That’s why ERVs are often recommended in more humid climates, such as in the southeast.

Martin Devit, owner, Thermal Associates, a mechanical contracting firm in Glens Falls, NY, says his company often offers HRVs to customers.

“It’s very profitable from a couple of standpoints,” he says. “First, you can make your mark-up on it, and you can make your labor on it. But if you can solve somebody’s problem — such as when their windows are all fogged up one day, you go and put in an HRV and the next day it’s nice and clear — you’re a hero.”

Not only that, Devit notes that due to word-of-mouth, secondary sales are huge. And once you get your foot in the door, these same customers usually return for add-on sales.

“When you solve someone’s problem, you develop a level of trust with that person. It’s very profitable,” says Devit.

When to offer an HRV

The need for continuous ventilation is everywhere, notes Steve Svien, indoor air quality products sales manager, Venmar-Broan-Nutone, Hartford, WI. Therefore, he believes contractors should always offer HRVs to their customers. Where customers will see a particular benefit is when someone in the home has persistent upper respiratory problems or asthma, or if the home has excess condensation on the windows.

“In many homes, people just don’t feel good, and it usually has something to do with the air in the home. An HRV improves comfort by changing the air about every three hours, and it keeps the air circulating inside the house. When the air conditioner or furnace isn’t on, fresh air is continually being introduced,” says Svien.

He says that HRVs are becoming more popular around the country and that business is growing tremendously.

Customers don’t seem to be balking at price, even though an HRV can run upwards of $1,500 for an average-sized house.

Devit says that installation is pretty simple, and selecting the right-sized unit is a breeze. There are usually only three different sizes to choose from — small, medium, and large. Svien notes that when selecting a unit, contractors need to figure out which unit to use by either:

  • the volume ventilation method, which is based on the overall cubic feet of air inside that home, or

  • the people method, which is based upon 15 cfm for each person inside that home.

“We have an installation instruction sheet with all that information. And there’s nothing like sitting down with a customer and running those calculations in front of them. It really makes a contractor look professional,” says Svien.

It’s also necessary to consider other factors, such as what type of heating and/or air conditioning system is in place and whether or not a large deal of moisture is present. If the latter is the case, an ERV might be a better choice. Again, manufacturers are more than happy to discuss their products.

HRVs typically run at two speeds. They have a 24 hour/7-day-a-week low speed, which provides the minimum amount of air changes to maintain comfort in the house. If somebody’s in the shower or the unit detects higher humidity, the unit increases to high speed. On some units there is even an intermittent setting, where it will run 20 minutes on and 40 minutes off. That’s a beneficial setting if the low speed setting is providing more ventilation than the house requires.

After selection and installation, the biggest issue with HRVs is balancing.

“Balancing the system is critical,” says Svien. “Make sure that the same amount of air is coming in that is going out. Contractors typically install HRVs, turn them on, and then walk away. That can create more problems.”

Svien adds that his company includes the correct balancing procedure in the installation manual. Other than that, there’s not much that can go wrong, says Devit. The only thing that can go wrong is if you don’t offer them to customers.

“Learn about indoor air quality and listen to what customers are saying. If they’re stuffy, or they have a lot of colds, or their windows are fogging up, then you know they’ve got a problem. And an HRV just may be the solution for it.”