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Does a HRV or ERV pay for itself in a pretty good house?

artisanfarms | Posted in General Questions on

I’ve been trying to learn about HRV and ERV systems and have found some payback analyses for larger commercial systems, and am wondering if they ever pay for themselves in a single family house with ~22,000 cuft living space (including the finished portion of the basement), or if it would be cheaper to just run a small ventilation fan occasionally, or crack a window?

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Replies

  1. MartinHolladay | | #1

    Artisan,
    The answer can be found in my article, "Are HRVs Cost-Effective?"

    1. artisanfarms | | #2

      Thanks for the link.

  2. Expert Member
    Michael Maines | | #3

    A Pretty Good House is relatively airtight--ideally no more than 1-2 ACH50, so mechanical ventilation is required--both by most building codes and by common sense. The question is whether you need balanced ventilation, exhaust-only, or supply-only. Ten years of crowd-sourcing information and opinions for what makes a PGH says that balanced ventilation is required, whether or not it has an attractive payback period.

    While exhaust-only ventilation systems can work, they also depressurize the home's interior, leading to things like increased radon infiltration, makeup air entering through random gaps and cracks rather than through a known filtration system, water infiltration and backdrafting of combustion equipment. There are work-arounds to all of those, but with what we now know about the importance of indoor air quality, and the availability of many good balanced ventilation options, if you're building a Pretty Good House, you should include an ERV or HRV, even if it's not the most cost-effective option.

    1. artisanfarms | | #5

      I'm not trying to be difficult, but what's wrong with cracking a window and running a small exhaust fan when you're in the house vs. spending thousands for a HRV or ERV?

      1. Expert Member
        Joshua Salinger | | #8

        An E/HRV has a number of functions. Building durability is one of the most important. By balancing the pressures between indoors and out, it reduces in/exfiltration of moist air into the assemblies. This can lead to moisture build up and biological growth-- which is a health issue. It also filters the air, which opening a window can't do. If there is high pollen, uncomfortable temps, noise, high/low humidity, rain/snow nearby traffic, etc., cracking a window is not helpful. This is also a health issue. Running an exhaust fan with an open window causes infiltration, poor comfort and energy losses. E/HRV's can also take stale air from 'dirty' places such as kitchens and baths and supply fresh air to living and bedroom areas where the people are. Opening a window is random ventilation, a balanced ventilation system is a strategic ventilation strategy. The short answer is that an E/HRV should not be, first and foremost, an economic return question, rather a durability, health and comfort concern. For instance, I have a son who has bad allergies. I couldn't care less about how quick the ROI of my economic investment is. Everyone has different but equally important issues and one needs to view the E/HRV question through this lens vs. just an economic one.

  3. walta100 | | #4

    My opinion is maybe in zone 6 & 7 where you will see very differentials between the indoor maybe 100° at times then yes, I think a dollar return on investment is possible.

    In zones 1 & 2 absolutely no way to see a dollar return on investment with a 30° differential.

    Walta

  4. Expert Member
    Akos | | #6

    The math on this is pretty easy.

    For example, I'm at 7200 heating degree days. A typical house will need around 100CFM of ventilation.

    Exhaust only ventilation the cost of providing this is:
    7200 HDD *24 hours * 100CFM * 1.08 (btu/cfm)=186 Therms.

    With an 80% efficient HRV/ERV that drops to:

    7200 HDD *24 hours * 100CFM * 1.08 (btu/cfm) *(1 - 80%)=37 Therms.

    So it definitely saves a fair bit of energy, even when heating with a heat pump, that adds up.

    The question is does a $20k ERV setup make sense? I would have a hard time justifying that, ROI is pretty much never. There are some ancillary benefits to a fancy ERV, so for some that might be worth the cost.

    Instead of a top of the line install, getting a higher efficiency ERV installed using simplified or hybrid ducting to the air handler return should be a reasonable ROI in colder climates.

  5. Walterwilkinson | | #7

    An HRV or ERV can pay for itself in a well-insulated, energy-efficient house by improving air quality while reducing heating and cooling costs. However, the payback period depends on factors like your climate, energy rates, and usage. For a house with 22,000 cuft of living space, these systems can be more cost-effective than relying on a small ventilation fan or opening windows, which may lead to heat loss or increased energy consumption. For managing your finances while considering home upgrades, check out https://thecashappapk.com/cash-app-apk-for-ios/, a great alternative to PayPal and Payoneer for saving and managing digital currency, including crypto.

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