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Q&A Spotlight

Why Is It So Cold In Here?

The furnace can put out plenty of heat, but the house feels cold unless the furnace is running

Baseboard-style forced-air registers like this one provide plenty of warm air in the 1950s single-story house, but the heat doesn't seem to end up in a place that keeps occupants comfortable.
Image Credit: Image #1: Whiskers / www.diychatroom.com

J Pritzen’s single-story Illinois house was built in the 1950s. It’s heated with a gas furnace fully capable of meeting the heating load, but somehow it isn’t getting the job done.

The single-story brick house has a mostly insulated, but unheated, basement. Warm air is distributed on the main floor by a series of floor registers set near exterior walls, and an energy audit tells Pritzen the furnace is cranking out 10,000 Btu more per hour than is lost through the walls and roof.

“Yet it’s not comfortable when the heat isn’t blowing,” he writes in a Q&A post at GreenBuildingAdvisor. “For example, my fingers and feet get pretty cold sitting typing on this computer even though the thermostat is happy.”

Pritzen has taken some temperature readings and discovered warm air is collecting at ceiling height, where it can be 13 F° warmer than it is at floor level. If the thermostat is set at 68°F, Pritzen’s feet will be in 59°F territory. If he could reach up and touch the ceiling, it would be 72°F degrees.

“My baseboard registers simply blow the air up, and most [of the registers] are right up under a window. (Makes me wonder if the heat is just going out the window instead of into the room),” he says. “I was wondering if there are any resources which describe what today’s guidelines are for maximizing forced-air system efficiency by register placement and diffuser selection, in case my home needs an update. For example, is there any reason for a home to really have 48-inch baseboard diffusers? Is that hurting or helping air mixing?”

Pritzen’s heating problems are the topic for this Q&A Spotlight.

Blame the stack effect

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11 Comments

  1. Alan B | | #1

    I've thought about this problem
    I have found that as long as all 6 sides are at room temp or have R5 (which keeps them at close enough to room temp) you will be comfortable. This is a rule of thumb, not an exact number. Heat vents near windows help keep them from feeling cold at a distance.
    As an aside i am curious at what point you no longer need the heat vent near the window, would R2-4 be sufficient?

    The house in question has cold floors, which will make quite the difference, determining the cause is a big step because i have a similar problem, i have 2/3 basement and 1/3 crawlspace and a single floor house. When i moved in all rooms were comfortable temp. However i later discovered that the crawlspace was getting lots of heat from a disconnected vent. When i plugged it the floor above the crawlspace became very cold, making that third of the house quite chilly, sounding similar to the OPs problem

    In my case the cause is simple but hard to remedy (cause is likely different from the OPs, but explained here for interest), there are gaps to the outside i can't reach because of the shallowness of the crawlspace, and the house is balloon framed and the crawlspace portion of the house is an addition, hence cold air comes in, gets "chimneyed" to the attic and out the attic vents cooling everything it touches, When it was getting loads of heat it kept the crawl and connected surfaces warm (at high energy wastage), but now the floors are very cold till i can fix the air leakage problem someday.

    An additional note, many furnace techs will tell you the "solution" is to run the furnace fan 24/7. They don't care about the energy cost, and will often start a huge argument if you even mention it, but it is a band aid solution that does often work because the always moving air helps warm cold surfaces, but at high energy cost.

  2. Ted Kidd | | #2

    "I write a blog, therefore I'm an expert..."
    "my fingers and feet get pretty cold sitting typing on this computer even though the thermostat is happy."

    How is the "thermostat happy" if the occupant isn't?

    "To GBA managing editor Martin Holladay, it's open-and-shut case.
    "The reason for the stratification you describe is almost certainly air leakage driven by the stack effect," he tells Pritzen. "The solution is to perform air-sealing work in your basement and attic."

    I wish I could physically slap you every time you say something stupid so you wouldn't say so many stupid things! You haven't even been to this house! Yet like Kreskin you know exactly what it needs?

    And when they've air Sealed, further reducing load and increasing short cycle time and temperature imbalances?

    Doing this correctly is work. Designing solutions that anticipate systemic interactions takes time. Jumping to design conclusions and making off the cuff recommendations fails on so many levels. One big one is you are dismissing a whole diagnostics and design profession as unnecessary. Another is you have no accountability for outcome failure of your recommendations.

    Stop. You are commuting malpractice AND insulting the building science profession.

    Ask yourself; "do I have any understanding of integrity or ethics?" If the answer is yes you must recognize the dissonance of prescription without diagnostics.

  3. User avater GBA Editor
    Martin Holladay | | #3

    Response to Ted Kidd
    Ted,
    If it makes you feel better, feel free to slap me next time you see me.

    I never said this is an open-and-shut case. Scott Gibson said that. I suggested a cause that I called "almost certain." Remember, I wrote "almost."

    It goes without saying that we are doing our best here at GBA to provide our best guesses without visiting the site. Our free advice is generally worth what you pay for it. If you find it irksome that we offer free advice even though we have no access to the job site, there is no reason to read our Q&A column.

  4. Alan B | | #4

    Agree with Martin
    My first thought on most of the questions is i wish i could see it first hand

  5. Expert Member
    Malcolm Taylor | | #5

    Forget it
    delete

  6. David Eakin | | #6

    What I Did
    In closely reading the description, it seems to me that the house in question is a block frame with brick facing construction (typically with 1x strapping on the interior to hang gypsum board/plaster - which would allow for the 1" insulation). I'm not sure that an EIFS system would be the preferred solution here due to the rain screen space between the brick facing and the block. In any case, what I decided to do for my home (double-wythe brick) was to create a second, inner framed/insulated/drywalled wall against the original cement-covered brick wall - creating extension jambs for windows and exterior doors. In our dining room, where there were too many complications to permit doing this on both exterior walls, I only created 1 "new wall". But it was on the North side of the house and was the largest exterior wall of the room. Even with this partial solution, we have experienced significant improvement in comfort. Yes, you loose some interior floor space, but you gain much in comfort.

  7. Jerry Wright | | #7

    how do you do that?
    "a window fan, a wet finger, and a $50 infrared thermometer can do a lot."

    Please tell us how we would do this. Thanks.

  8. Mark Heizer | | #8

    Mixing and stratification
    From the look of the baseboard grilles and the likely age of the system, there's more to this than just leakage. My guess is that the furnace is putting out very hot air through grilles that aren't providing mixing. There's not enough velocity out of the grilles to mix thoroughly (from back in the day when most installers relied on natural buoyancy and old octopus furnaces were still common). Overhead heating delivery should never be more than 10-20F warmer than the space. For floor delivery, if you're putting out 120F air, it's shooting to the ceiling without mixing at all. Thus the stratification. You can put out as much heat as you want, but at thermostat level, you'll only get "warm" after the air at ceiling level is hot. And yes, this drives faster exfiltration, which is the reason the home is inefficient. But if you want comfort: Better mixing and lowered delivered supply temp. = increase fan speed if possible, get a grille that mixes the air, one time where ceiling fan might help. Get the supply air temp where the delta is reasonable.

  9. Ed Henderson | | #9

    Cold near floor
    I live in a 1100 sq ft home built in 1973-4. It is what we call up here in Calgary a raised bungalow. The original Natural gas furnace is still heating my home.
    We leave the furnace fan on from Sept to about mid May. When we developed the basement a very senior carpenter who helped and directed the job insisted that we install cold air returns at basement floor level in the basement.
    Our home has additional insulation in the top ceiling,,about R 40 up there. Our home is cozy and warm all winter long. Our TV room is in the basement and we can lie on the floor down there when it's 25 below outside.

  10. Kathleen Sisco | | #10

    right up my alley
    I wish I had my Henderson's elderly carpenter here. I think that my house was originally done by an elderly carpenter as the original heat was a metal wood furnace with built in hot water tank. Replaced by gas Goodman 46,000 btu Hi Eff 92% using same ductwork only the heat now is blown from the cold air returns as the wall ducts are a foot off the floor and perhaps stripped the heat. The wood probably heated the entire basement up. Not so with that cold-to-the-touch gas furnace.
    I agree with this discussions point of the walls being a source of leakage. Especially under the windows. Why infra red scans are not required I do not know.
    Following is post: I moved into 1,000 sq for one level ranch that is 65 years old or more. Looks modern. Originally had alum siding and maybe the insulated windows are original. For some reason, I suspect elder abuse, the siding was removed and replaced with vinyl. This is my second winter here; my inspector told me it needed more insulation but I looked at the attic and iffy. But here at Feb 2016 I see the frost on the inside bottoms of the windows and feel the cold sills I realize that when they pulled the alum off they were careless.

    To explain why I feel this way I lived in Duluth in the subsidized towers and while there the agency 'upgraded' the slide bys to crank outs. While it was supposed to save money I myself witnessed the unnecessary removal of a fiberglass insulating strip --4x 36--being pulled out and tossed from the bottom of the window in the space between the window frame and the wall stud. The company had rented a crane --we were an 8 story building--and maybe didnt want a breeze to blow this out in their way or compromise the timely removal and insertion of the new windows. I saw first hand that there is no understanding of the need to consider all facets. The agency would have bigger light bills, we residents would be hotter and colder all because of this attitude. If I had not seen it I wouldn't have believed it.

    Here the black mold on the aforementioned windows is now understandable. There is air leakage not from the house inside but from underneath the windows where the insulation was removed or just settled. The sill is very cold. In order to verify this lack of insulation I would have to pull off the siding and backing board and black paper wrap AND maybe the original wood siding. There is no obvious way to do this otherwise. Guessing by drilling holes and pumping in foam is not acceptable after all the work of removal.

    The issue of moisture barrier is also complicated. Originally the plastic wrap should have been ON THE INSIDE WALL BEFORE DRYWALLING as putting up a moisture barrier ON THE OUTSIDE OF THE STUDS TRAPS MOISTURE IN.

    Which seems to be what I have. I have yet to see a forum that makes it clear that putting up a moisture barrier on the outside of the studs is pointless and even damaging. Because it seems that no one wants to pull off all that wood. And then how would you put in a plastic wrap? Well, you would have to use fiberglass batts that are plastic wrapped wouldn't you? That would at least reduce the moisture getting to the outside but not completely as it could pass into the wood studs.

    What do contractors say about this?

    My issue is the electric bill, $250 and gas for heat $68. So I am blaming the fan running constantly.

    And there is the claim that heat loss is over 80% thru the ceiling into the attic so why go to the cost of redoing the entire siding.

    I feel that Rural Development should long ago have required infra red scanning of the winter high use month in their loans. Why constantly discover a problem when it can be noted and included in the loan papers? This is yet another hidden issue that is being allowed to be invisible like easements covered by the wording 'any and all' or non-disclosure of fill.

    Sincerely
    Ms Kathleen Sisco
    1126 N 9th Ave
    Iron River MI 40035

  11. Kathleen Sisco | | #11

    more
    Just so you know, there are other problems I have dealt with a few, like drafty doors. My first winter here was 70 degree humidity in uninsulated basement, this winter 50. Upstairs with this below zero (20 below) now 30 RH. So the humidity is not from the house. Here there is nearly always high humidity outside. Last year heating was a nightmare constantly cold even with liv/din blocked off. Thermo set at 58-62. Heated one small room with mica panel. Basically lived in it. Almost no reduction in elec cost.
    This winter tried blocking vents, nearly died from CO. Used two elec heaters--no fan--for month of mild December with all room vents blocked except for kit/hall/bath--one oil filled heater in kit--and my little room--one mica heater. Furnace off at circuit breaker. Result $350 light bill. Gave up turned furnace on, unblocked all vents except my little room, set thermo at 66. Light bill for warm house $250. But Feb elec bill might be the reason the house was foreclosed.
    Social security precluded second mortgage for boiler/hot water system which is my choice.
    I have you tube house videos under katesisco.

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