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Community and Q&A

Do I need an HRV/ERV for a house built in 1947?

will82 | Posted in Mechanicals on

I have a three-bedroom house, one bathroom, in Worcester, Massachusetts. It was built in 1947, and measures 1,100 s.f.

After purchasing it, I decided to upgrade the insulation in the walls and in the attic and air seal the home, and install new windows. All which was done through the Mass Save program. After completing, all the energy bills went down.

But the problem now is the house has high humidity and seems to be too tight and cause hard breathing. I have noticed mold that I did not have before. Also get headaches more often than I used to.

I think they should let people know after they do all this work they may have fixed one problem but created a new one.

Not sure how to fix this problem. The only solution I think is to install a Panasonic Intelli-Balance 100, Balanced Air Solution, Cold Climate ERV, 50 to 100 CFM.

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  1. GBA Editor
    Martin Holladay | | #1

    You raise many questions. I'll try to answer as many as I can.

    The first issue concerns whether the Mass Save program ignores the need for residential ventilation. As far as I know, the Mass Save program encourages compliance with ventilation requirements. See, for example, the following Mass Save document: "Residential Ventilation System Requirements."

    That document notes that the Mass Save program offers free phone assistance at this number: 855-757-9717.

    In the case of your Mass Save work, I'm not sure what was determined. You haven't told us whether a blower-door test was performed after the work was completed -- or, if so, what the results were. So I'm not sure whether your house is "too tight." It might be, but we're guessing.

    If you know the results of a blower-door test, you should tell us what those results were.

    In general, when air sealing measures are performed on an older house, it's a good idea to perform a blower-door test. If the results show that the house is now very tight, installing some type of ventilation system would make sense.

    Concerning your problems:

    1. If you are having difficulty breathing and you are suffering headaches, you have medical symptoms. By all means, see a doctor. The building experts and energy experts at GBA are not qualified to help you with a medical problem. Your symptoms could be indications of many possible issues, so please consult a doctor to assess the situation.

    2. If you suspect that poor indoor air quality is contributing to your symptoms, you should operate one or more of your bathroom exhaust fans for 24 hours a day. This type of ventilation approach is called "exhaust-only ventilation." This may entirely solve your problems, so it's worth trying.

    3. The ERV you mention from Panasonic is just one possible brand of ERV. There are other options. For a full discussion of mechanical ventilation, see these two GBA articles:

    Designing a Good Ventilation System

    Revisiting Ventilation

  2. will82 | | #2

    Thank you Martin for some answers.
    They did not complete the blower door test when they left. Went to the doctor he asked what has changed my life. I let him know about the home and he recommended to hire a contractor to take a look at it. I have attached a picture that shows some of the problem. Which did not happen before they insulated and air sealed.

  3. GBA Editor
    Martin Holladay | | #3

    Start by operating one or more of your bath exhaust fans for 24 hours a day. See if that helps.

    You might also want to purchase a hygrometer to measure indoor relative humidity levels. It's possible that your indoor air is humid. If measurements show that to be the case, the usual remedies include (a) increasing the ventilation rate, and (b) identifying and correcting the moisture sources inside your home.

    For more information on lowering indoor humidity levels, see "Preventing Water Entry Into a Home."

  4. Expert Member
    Peter Engle | | #4

    Enough humidity to cause condensation like that on insulated glass, associated with headaches and trouble breathing can be symptoms of carbon monoxide poisoning. You might have a disconnected vent on a combustion appliance, or a blocked chimney. You should ventilate the house immediately. It is summer now, so open the windows and leave them open. Contact a HVAC contractor right away to check your vents.

    Other than that, the article Martin mentioned is a good one. Look for sources of moisture in the house. We basements and crawl spaces, or crawls with dirt floors are often big moisture sources in homes of your age. It should be obvious, but you should not be running a central humidifier on your HVAC equipment. Beyond that, the moisture of living may be adding up: cooking, cleaning, bathing and breathing all add moisture. Consider all of these sources and address them one by one, then add ventilation.

  5. will82 | | #5

    The only appliance is a condi boiler which was inspected recently. The home is baseboard heater forced hot water basement floor are concrete. The company (Clearesult)that did the inspection is going to reinspect. Will update after inspection. I did think about running a dehumidifier but think the Panasonic ERV would help more since this was not a problem until the house was insulated and air seal. Just trying to come up with a solution for under $1000.

  6. GBA Editor
    Martin Holladay | | #6

    It's hard to come up with a solution before you have a diagnosis. After you purchase one or two hygrometers, tell us what the interior RH is.

    Note that while operation of ventilation equipment helps lower the indoor RH during the winter, you generally can't use the same approach in summer weather -- especially hot, humid weather.

    If it's true that you have higher indoor RH, the way to lower the indoor RH during hot, humid weather is to minimize the ventilation rate and to operate an air conditioner or dehumidifier (assuming, of course, that you have identified any sources of moisture and done your best to minimize these sources).

  7. Expert Member
    Dana Dorsett | | #7

    Most summers in Worcester MA you can't keep the indoor RH under 50% with ventilation alone, but most of May/June this year that has been possible. Come July the outdoor dew points will likely average in the mid-60s F (like most years), which at an indoor temp of 75F is a sticky-uncomfortable 71% RH. If that window condensation picture was in recent weeks your indoor RH is likely to be even higher.

    No matter what you can SURELY keep the indoor below window-condensation levels with ventilation, in any season, but not necessarily in the human-healthy 30-50% range in summer without some air conditioning (or other mechanical dehumidification.)

    This house almost surely needs active ventilation, but you would be able to tell by running the bath fan continuously for a day or so. A couple of $10 AcuRite humidity & temperature monitors (available at most box stores) are good enough instrumentation to tell if you have a problem (as if you really needed it.) A real hygrometer would be able to measure it with higher precision, but for your purposes the cheap monitors are good enough.

    BTW: A tight 1100' 2x4 framed house with code-min windows usually has a heat load somewhere near the minimum firing rate of most wall hung combi-boilers. Most houses that size won't have enough baseboard to be able to operate in condensing mode without excessive on/off cycling or even efficiency & longevity killing shorty cycling. Too many installers just set it up for 180F output (well above the condensing temperature), and leave it up to the homeowner to figure out how to operate it most efficiently.

    For purposes of optimizing it, which combi boiler model is it, and how many feet of baseboard do you have? Also, if you have some wintertime gas bills, run a fuel-use based heat load calculation on it. For details on how that's done, see this bit o' bloggery:

    If I had to guess (and without any real data I kinda have to guess) I would expect the fuel use heat load numbers to come in between 14-18,000 BTU/hr @ 5F outdoors (Worcester's 99% outside design temp), 68F indoors. Most combi boilers big enough to support a couple of simultaneous showers don't even modulate much below 18,000 BTU/hr, but that's not a disaster if you have enough baseboard to run in condensing mode.

  8. will82 | | #8

    The Combiboiler is a lochinvar noble 120 minimum fire at 11,000BTU baseboard 60 feet high output and 16 feet of regular. Also has an outdoor reset temperature does go up and down depending on the outside temperature. Gas bill was around $90 to $120 a month. Photo attached of the boiler. I guess the main question I am trying to ask is would I benefit by installing the Panasonic ERV. Or would it be a waste.

  9. Expert Member
    Dana Dorsett | | #9

    A Panasonic ERV would not be a waste. Depending on how the floor plan works or where the ducting might be routed it may be easier to install a ductless Lunos Nexxt or e2. (At 22 cfm the Lunos e2 wouldn't quite meet the 30cfm MA requirement, which is based on the arguably overly-ample ASHRAE 62.2, but it would still be good enough for most homes your size.)

    Most people are reluctant to in stall a wall-hung water heater with only ~100,000 BTU/hr of burner in a location with Worcester's wintertime incoming water temperatures, but the 11K min-fire input (~10,500 BTU/hr out at condensing temperatures) is pretty good. That's enough burner support a single full flow shower in the dead of winter, but not two.

    There is no industry standard definition of "high output" baseboard, but with 76' of baseboard total that's 10,500/76= 138 BTU/hr per foot which is low enough to support operating at condensing temperatures without short cycling, assuming it's operated as a single zone, even if it were all run of the mill 1.5-2" fin-tube.

  10. Expert Member
    Dana Dorsett | | #10

    In looking over the specs for the Panasonic WOULD be a waste.

    The Intelli-Balance 100 minimum air flow of 50cfm is too high for an 1100' house for continuous operation. Without duty-cycling it on/off you would be overventilated, with excessive wintertime drying. Ideally you would be able to run the ventilation continously, and be able to adjust it's speed seasonally for optimal comfort & air quality.

    The MA requirements for a house your size would be between 30 cfm max (1-BR) to 45 cfm (2-3 BR):

    Operated at the MA requirement levels will cause excessive winter drying, and would add to the summertime latent load. While it's good to be able to crank it UP to those levels if/when air quality is suffering, operating at something like half that is usually more than enough to manage moisture and keep indoor air quality high for non-smoking households. The Intelli-Balance 100 won't be able to dial down to a more appropriate ventilation level for your house.

    A Lunos e2 would deliver 75% of the MA requirement for a 1-BR house your size, or half the MA requirement for a 2-3 BR house and is almost certainly enough. It can be throttled back if the wintertime air is getting too dry, and even at the max speed won't be a large latent-load adder.

    A continuous operation 20cfm bath fan (eg: Panasonic FV-04WS2 ) would meet code as adequate bathroom ventilation. Used in conjunction with a Lunos e2 you would be at 42cfm total, which fully meets the MA ventilation requirements for a smaller than 1500' 1-BR, and would be at 93% of the MA requirements for a 3-BR. Turning the Lunos speed down or off would allow finer granularity of the total background ventilation settings without having to duty-cycle it the way you would need to with an oversized ventilator.

    Using kitchen & bath ventilation whenever cooking or bathing is really mandatory in tight houses for managing humidity and odor inputs. With 20cfm continuous the bathroom's ventilation is covered, but you'd still need to use kitchen ventilation while cooking (and for 15-30 minutes post-cooking, depending on the meal.)

    Barring further information, that seems like the best fit. It's a fairly open floor plan you might consider doing it with a single ductless TwinFresh Comfo RA-50 or RA1-50-2 (3 speeds: 8cfm , 16cfm, & 32cfm), but a Lunos e2 would give you more guaranteed mixing, with two points of active ventilation.

  11. will82 | | #11

    Thank you Dana
    I do have a 700 square-foot basement unfinished my plan was to dump 10 CFM‘s in the basement and the other 40 CFM‘s upstairs in the main living space would this work? Just looked at the price for the Panasonic FV-10VEC1 found it for under $700 I would like to stay at this price point. Also what if I turn down how often it cycled would that help? I know this model can do 10 20 30 40 50 60min cycles.

  12. Expert Member
    Dana Dorsett | | #12

    Even with the basement volume included 50cfm continuously would over-dry the place in winter. Duty-cycling it at 20-30 minutes/hour or less would probably be about right, or even 10 minutes /hr during cold snaps.

    Properly designing / installing /commisioning the balanced duct system would be the next step if going with a ducted ERV.

  13. will82 | | #13

    Lunos e2 looks like it would work but expensive and the Panasonic FV-04WS2 looks like a good price but not very efficient. Is there any other options low CFM‘s and good heat recovery for a good price?

  14. Expert Member
    Dana Dorsett | | #14

    When comparing the cost of the Lunos e2 to fully ducted systems you have to consider the cost of the ducts as well.

    The FV-04WS2 is exhaust-only ventilation, but at just 20cfm it doesn't add up to a huge heating or cooling load. It would only be "necessary" if you wanted to go with the Lunos e2 (22cfm, max) and needed more cfm merely to comply the MA 30 cfm spec for 1BR houses under 1500 square feet.

    If meeting the MA requirement isn't a goal, either a FV-04WS2 or an e2 alone should be enough to deal with the excessive humidity issue if operated continuously.

    The MAJOR difference between them would be that with the FV-04WS2 you don't have knowledge or control over where the ventilation air is entering the house, which isn't guaranteed to be a clean, uncontaminated path. With the Lunos e2 the bulk of the ventilation air is coming through the Lunos units.

    If you're using both together, the major air source will still be through the Lunos (even the air pulled in by the FV-04WS2.)

  15. Peter L | | #15

    I have the Ultimate Air ERV and yesterday I ran it during the day:

    98F outdoor temp
    74F indoor temp
    80F fresh air discharge

    It's pretty efficient judging by the above results. My indoor humidity was at 40%

  16. will82 | | #16

    Seems to be some confusion on HRV vs ERV. My question is do I need an HRVOr ERV for Worcester Massachusetts house has high humidity in Spring summer and fall (60% to70%RH) inside was using a DH in the basement it would cost a fortune to run one in every room of the house.
    Winter is average humidity in the home. Attached or maps One says ERV the other one says HRV.

  17. GBA Editor
    Martin Holladay | | #17

    Both maps are wrong. For the real story, read this article: "HRV or ERV?"

  18. Expert Member
    Dana Dorsett | | #18

    In Worcester MA the ERV vs. HRV really doesn't much matter unless you require MASSIVE ventilation rates in summer, and have extremely low cooling loads (or no air conditioning.)

    In my house (ZIP code 016xx) a half-ton window-shaker AC has no problem keeping up with the latent loads of the 2400' of above-grade conditioned space, including the additional load of (non-ERV) ventilation. At fewer than 350 cooling degree days the additional power use of that small increase in cooling load doesn't add up to much.

    In the ~1600' of basement I have pair of Lunos e2 and a standalone 70 pint dehumidifier (which I haven't even plugged in so far this year, but I might this coming weekend, given the forecast for dew points edging close to 70F.)

  19. will82 | | #19

    Here are the three options that I was looking at Panasonic FV-04VE1 or Panasonic FV-10VEC1 or the
    Lifebreath RNC5-HEX-TPD Residential Heat Recovery Ventilator (HRV) Just want to make sure I am making the right choice. I know two of these units will require running ductwork. By doing this I will also be able to even leave my basement which is 700 square-foot unfinished. The Panasonic FV-04VE1 would only be able to cover the main part of the house. Home does not have AC only window units. Any input would be appreciated thank you.

  20. GBA Editor
    Martin Holladay | | #20

    The formula stipulated by ASHRAE 62.2 (the nationally recognized residential ventilation standard) calls for your house to be ventilated at 63 cfm.

    For more information on the ASHRAE 62.2 formula, see "Designing a Good Ventilation System."

    The maximum supply air flow of the Panasonic FV-04VE1 is only 30 cfm.

    The Panasonic FV-10VEC1 is rated at 100 cfm, while the Lifebreath RNC5-HEX-TPD is rated at 89 cfm. If you selected one of these two appliances, it would meet the minimum ventilation rate set by ASHRAE 62.2.

    Of course, some homeowners choose equipment that won't quite meet ASHRAE 62.2, and it's possible to make a case that the ASHRAE 62.2 ventilation rate might be too high. But if you choose undersized equipment, you should do so with your eyes open.

  21. Expert Member
    Dana Dorsett | | #21

    ASHRAE 62.2 need not apply. Click on the "Residential Ventilation System Requirements." link in response #1.

    MA code calls out only 45cfm on a house that size if it's a one bedroom...

    ...and 60cfm (not 63cfm, per ASHRAE) only if it's 2-3 bedrooms (and more if it's more than 3).

    When 20-40 mode is selected max air flow on the FV-04VE1 is 40cfm, just shy of the MA spec:

    Even at 0.1" w.c. the exhaust flow is still 40cfm even if only 30cfm is coming out of the unit's supply, so the net ventilation is still 40cfm,- the other 10cfm is being pulled in from other air leaks in the house.

    That said, the Panasonic FV-04VE1 is not as appropriate for 1100' of conditioned space unless it's a wide-open floor plan and the unit is located centrally. With that unit there is only a single exhaust & supply, co-located within inches of each other. Even at lower total cfm a Lunos e2 can do a better job of distributing the ventilation air if the pair is well separated, since there are two locations delivering 11cfm (average) each.

    Worse still, the FV-04VE1 auto switches to primarily exhaust only mode when it's cold outside: It runs a 33% exhaust-only duty cycle between 20F and 30F, that drops to 86% exhaust-only when it's below 20F (see the Frost Prevention Mode in the sell-sheet) , and is thus not recommended for wintertime use in a MA climate. (The mean temp in Worcester MA in January is ~25F.)

  22. GBA Editor
    Martin Holladay | | #22

    I agree -- but note air volume supply specs below.


  23. Expert Member
    Dana Dorsett | | #23

    Exactly- it's not a balanced ventilator. So?

    The supply output at the unit supplies 30 cfm of the 40, air infiltration delivers the other 10cfm. The total ventilation rate is identical having a 10cfm exhaust-only fan in addition to a perfectly balanced 30cfm ERV. A 40cfm exhaust-only (NO direct supply air) would also be the same from a ventilation compliance point of view. The fact that only 30cfm of this unit's 40cfm ventilation capacity is getting the benefits of energy recovery is moot- only the total ventilation rate matters to code officials.

    Being that this house is a 3 bedroom means the ventilation needs to be capable of delivering 60cfm to be in compliance with the letter of MA code (even if only one person is actually living there), even though less than half that would be sufficient to fix the humidity build-up issue. A single Lunos e2 pair plus a 40cfm exhaust-only fan would meet that spec, so would an FV-04VE1 plus a 20cfm fan. (The 20cfm fans designed for continuous operation in bathrooms such as the Panasonic FV-04WS2 are specifically marketed get around the alternative requirement for higher cfm bath fans operated intermittently). There is nothing that says you must operate any or all of the ventilation continuously.

    A continuous ventilation rate of even 22 cfm (a Lunos e2 at max speed) is 31,600 cubic feet per day, which for this house would be about three complete air exchanges per day. Unless there's always a pot o' pasta boiling on the stove or 10 people showering every day without benefit of bath fan, that should be enough to keep the indoor humidity bounded. A 60cfm rate (the MA code prescriptive) pr 63cfm (ASHRAE) is closer to 10 air exchanges per day, which would be excessively drying in winter, and not really necessary for most non-smoking homes (and maybe not enough for a house with three smokers with a pack-a-day habit each.)

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