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Community and Q&A

Installing an HRV retrofit

Sara Mattox | Posted in Energy Efficiency and Durability on

We have a 26 year-old home, that according to an energy audit, is too tight. It is a split level with the basement finished. We were told that we would need to install an HRV. However, we live in North Pole, Alaska and our heating system is a baseboard boiler system, hence, no ductwork. We get plenty of condensation on our windows in the winter (almost a foot last year), mold in the bathrooms (bath fans are old and not moving enough air), and our oven vent just recirculates the air, doesn’t acutally move it outside. I’ll be honest, my DIY skills are limited and $10,000 for someone to come in to do it for me isn’t feasible at the moment. Are there any suggestions on where to start or other options? I am terribly desperate at this moment. Just remember that 50 below is not uncommon for where we live and anything and everything is more expensive here than anywhere else it seems, but I am open to any suggestions! Thanks so much for your time!

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Replies

  1. Minnesota Kid | | #1

    Sounds like you may need a 5 hour road trip to affordably pick-up the materials you need to finally solve the issue. I'm too green to plan all this out for you, but the HRV may be worth while to reduce moisture without leaving windows open and reduce heating costs. Door vents may help let air circulate among rooms with doors closed where ducted vents are to much work & cost. Until you save up, plan out, and study enough to DIY install an HRV using phone support I figure you can refine how you manually manage the moisture and venting out of the house.

    The good news is that a properly placed leak or thermal bridge can condense excess moisture, as your windows do so well. More can drip to a drain in the bathroom or kitchen where much moisture is released. A chilly window opening and vent out after ones shower can help settle the moisture before spreads to the rest of the house. Venting the stove fume hood directly out is a vital step. Be sure you ALWAYS open any window needed so the vented air is replaced before venting, or you may suck back draft air in through a water heater or boiler. Hopefully efficient & effective new exhaust vent fans are locally available. Cleaning fan vents & ducts regularly to reduce mold is a needed health step until moisture levels are better managed.

    I'm basically recommending freeze drying the bathroom regularly by completely exchanging the air with outside. Increasing thermal mass will facilitate recovering a tolerable bathroom temperature afterword. Rock should be available. A sealed water vessel is great if it never freezes solid or contributes moisture.

    Even with reasonable humidity the temperature of your window panes when it is -50F, is vital to reducing condensation there. I assume windows are tight because the house is "too tight". Good Storm windows can add R-2 for less than replacing all windows with smaller U<20 ones. assuming it is coldest at night, diy insulated external shutters might be worth while (poyisocyaneurate rigid board with aluminum foil as radiant barrier may available). internal plastic window film help if then warm enough that water condenses without freezing so can drip into a container (you empty).

    Energy bills are likely high enough that an HRV for a super-tight house will pay for itself once you find a way to buy and properly install it with any enhancements to internal air circulation needed. Much of what makes everything more expensive there makes the marginal cost of buying the best quality equipment relatively less. The key is sustaining your finances and health until you can afford more user friendly home climate control equipment.
    Surely, others here can correct my most ludicrous suggestions.

  2. GBA Editor
    Martin Holladay | | #2

    Sara,
    HRVs are routinely installed in homes with hot-water heating systems like yours. You HRV will require dedicated ductwork; most of the ducts will be only 4 inches in diameter.

    Ideally, the HRV will pull exhaust air from the bathrooms and laundry room, and in some cases from the kitchen (although never from a range hood), and it will supply fresh air to your bedrooms and living room.

    In the lower 48, it's possible to buy an HRV for well under $1,000. Of course I don't know what it will cost in North Pole, Alaska. Installation is extra.

    To learn more about installing an HRV, read "Installing a Heat-Recovery Ventilator."

  3. John Klingel | | #3

    Sara: A FOOT of ice? A#1 I'd get those useless fans into a dumpster and get some air moving out of your bathrooms and kitchens, either with fans on timers or slowly, 24-7. Brown's Electric sells the Panasonic Whisper Green fans and they are as quiet as you hear them advertised (the one I have sure is), and they are somewhat programmable. Spenard's sells the American Aldes Airlet 100s passive air vents, I believe, which one of the gurus here suggested be used with exhaust-only ventilation systems. A few passive air vents (Aldes, for ex) and a few good, quiet fans, should go along way to reducing your moisture w/out needing a direct hookup to a fuel line from the refinery. Forget the btu's you are shipping out to the ionosphere. That ice and mold will generate huge bills for you sooner or later. In the meantime, I hope you are able to kill the mold w/ bleach; otherwise, a pro mold shop may be in order. BTW: Did you call Holaday Parks and ask them for suggestions? Ask for Jerry. john

  4. Riversong | | #4

    Sara,

    If your house is 26 years old it is probably not all that tight. The problem is that you aren't evacuating the primary moisture sources. You must replace the ineffective bath fans with quality, efficient units like the Panasonic Whisper series (http://www.energyfederation.org/consumer/default.php/cPath/30_85), and you should replace the fan wall switch with a timer switch so that the fan continues running for 15 minutes after showering (http://www.energyfederation.org/consumer/default.php/cPath/39_766).

    A recirculating range hood is worthless. You must replace that with an quiet, efficient vented hood (150-200 cfm is plenty) and make sure it's used while cooking (keep lids on all pots).

    Make sure the dryer is vented outside and the duct or wall cap is not plugged with lint. Make sure the basement or crawlspace is not damp.

    Do not dry cordwood indoors or wash the dog or water dozens of large potted plants or hang laundry by the woodstove, and if you have a jacuzzi don't use the jets.

    If you control the moisture sources, you may find that you don't need to install an HRV.

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