HRV & ERV Systems near you

DOE's Building America guidance puts the deciding question simply: the primary difference between an ERV and an HRV is that ERVs transfer moisture as well as temperature, so the question to ask is whether it is usually too humid outdoors. In hot, humid climates an ERV may be the better choice, because moisture and heat both pass from the incoming air to the outgoing air, so the air arriving indoors is somewhat cooled and dehumidified. In cold climates an ERV can help retain moisture within the home and potentially improve comfort in houses that get uncomfortably dry in winter.

The reverse case is just as real. In hot, dry climates Building America describes a similar split, where larger or leakier homes with low moisture generation may benefit from an ERV to retain indoor moisture, while smaller, tighter homes with higher occupancy may benefit from an HRV to reduce indoor humidity. And in mixed climates it notes there are many situations where an ERV is more beneficial during the cooling season while an HRV is more appropriate during the heating season, which is an honest way of saying the answer is not always clean.

For cold-dry conditions the guidance is more direct. Building America's code brief on heat recovery ventilation states that HRVs are recommended for cold-dry climates and are most cost effective in climates with extreme winters where fuel costs are high. Whichever you choose, the same guidance tells designers to see the manufacturers' specifications for determining which model is best in which climate and to install it according to their directions, especially in regard to ERVs in humid climates.

Two questions decide the specification: does the house need mechanical ventilation at all, and how much. On the first, Building America's code brief quotes the residential code requirement that a dwelling unit testing tighter than five air changes per hour with a blower door must be provided with whole-house ventilation. On the second, the same brief reproduces the model code's continuous whole-house mechanical ventilation airflow table, which begins at 30 cubic feet per minute for a dwelling of less than 1,500 square feet with no more than one bedroom and climbs with both floor area and bedroom count, with an intermittent-operation alternative that raises the rate in exchange for a shorter run time.

Recovery performance has its own ratings, and they are not interchangeable. Building America explains that Apparent Sensible Effectiveness is the most commonly published rating for heat recovery during cold weather, and advises looking for ASEF values above 80 percent, with the most efficient systems above 90 percent. Total Recovery Efficiency is the figure listed for ERVs, accounting for sensible and latent recovery during the cooling season, and the guidance is to look for TRE values above 50 percent. Comparing an ASEF number against a TRE number tells you nothing.

Code editions and state amendments differ, so confirm what your jurisdiction enforces and what it requires to be documented. Ask whether the installer will measure and record the delivered airflow rather than quoting the rating on the box, because the two are frequently not the same.

A balanced system is only balanced if someone balanced it. Building America notes that ventilation systems, including exhaust-only systems and improperly balanced ERVs and HRVs, can depressurize a home by pulling more air out than they bring in. In a house with a natural-draft furnace, water heater or fireplace, that is a combustion safety question rather than a comfort one, and it is the reason the supply and exhaust flows should be measured rather than assumed.

Cold climates add frost. When very cold outdoor air meets warm, moist exhaust air across a core, condensate can freeze, and units sold for northern service manage it with defrost cycles, preheaters or recirculation. A unit chosen without regard to that will ice up, lose airflow and, in the worst case, be switched off by a frustrated owner. Ask specifically how the model handles frost control at your design temperature, and where the condensate drains.

The commonest failure is neither of these. It is a system that was installed, commissioned and then never operated, because the control is in a mechanical room, nobody explained it, and the fan noise was mistaken for a fault. If your home has a recovery ventilator, find the control, confirm what schedule it is running, and put the filter change on a calendar. A unit that is off delivers exactly the ventilation of an unopened window.

These are simple machines with a small number of serviceable parts, and nearly all of their problems come from the parts that collect dirt. Building America notes that many systems require periodic cleaning or replacement of heat exchange media, filters and other parts prone to collect dust and dirt, and that the outdoor air intake should be located in an accessible place for maintenance, which includes cleaning to remove debris.

EPA's consumer guidance on radon reduction, which treats heat recovery ventilation as one reduction technique, is more specific about the schedule and is a reasonable baseline for any unit. It states that the filter in an HRV requires periodic cleaning and should be changed twice a year, that the vent bringing fresh air in from outside needs to be inspected for leaves and debris, and that the ventilator should be checked annually by a heating, ventilating and air conditioning professional to make sure the air flow remains properly balanced.

Two habits catch most of the rest. Look at the exterior hoods each season for insect screens, lint, nests, paint overspray and snow, since a blocked termination unbalances the system instantly. And keep the condensate drain clear on units that produce one, because a drain that backs up during a cold snap is how a core gets damaged.

Because radon enters from the soil and is diluted by outdoor air, ventilation is genuinely part of the radon toolkit, and EPA lists heat recovery ventilation among the radon reduction techniques that can be used in any type of home. Its description is careful: an HRV, also called an air-to-air heat exchanger, can be installed to increase ventilation, which will help reduce the radon levels in your home, and if properly balanced and maintained it ensures a constant degree of ventilation throughout the year. EPA adds that HRVs can also improve air quality in homes that have other indoor pollutants.

The limits are stated just as plainly. EPA notes that HRVs can be designed to ventilate all or part of a home but are more effective in reducing radon levels when used to ventilate only the basement, describes the effectiveness as limited by radon concentration or by the amount of ventilation air available for dilution, and flags that there could be a significant increase in heating and cooling costs, though not as great as ventilating without heat recovery. It also says an HRV used for radon control should run all the time.

The contrast with simply opening windows is instructive. EPA states that opening windows, doors and vents on the lower floors increases ventilation and can reduce radon levels, but that once they are closed, radon concentrations most often return to previous values within about 12 hours, which is why natural ventilation should normally be regarded as only a temporary radon reduction approach. If a test has come back high, treat ventilation as one option among several and have a mitigation contractor look at the house.

Building America is candid that the range of ERV and HRV equipment costs is quite wide, and the installed price varies more than the equipment does. The variables are whether the unit gets a dedicated duct system or shares the existing one, how many rooms are served and how far from the unit they are, where the unit can be mounted and whether power and a drain are already nearby, the core type and rated effectiveness, the controls and whether the unit is tied to a thermostat or humidistat, frost control in cold climates, the exterior terminations, and whether commissioning with measured airflows is included. Ask for the measured flows at handover, not the catalog rating.

LokalMatch is where the search starts. You describe the house once: how tight it is and whether it has been blower door tested, how it is heated, whether there are natural-draft combustion appliances, what the winter and summer humidity feel like, and whether any ventilation exists now. Ventilation and HVAC contractors serving your area receive that request and the interested ones contact you directly. Pros pay for the requests they receive, and homeowners use the service free. LokalMatch does not install ventilation, does not set prices, and does not vet, rank or recommend any contractor, so checking licensing and the commissioning scope stays with you.