Page 1 of 2 12 LastLast
Results 1 to 13 of 15
  1. #1
    Join Date
    Aug 2011
    Location
    Kingston, Ontario
    Posts
    207

    Attic Bedroom hot - Any suggestions?

    Our home is mainly on single level but we have one attic bedroom served by a stairway.

    We have a 3 ton central heat pump with insulated ducts running through attic space to most rooms. We have two air returns one of which is about 2/3 way up in stairwell near door of attic bedroom.

    There are two 6x12 air supply registers in the 15x10 attic bedroom. They are low down because ducts run through the wing wall cavities.

    Only the end wall with window and a small part of the ceiling have a roof directly above. The rest of the ceiling has unfinished attics one each side (House is Tee-shaped). Those attics have static roof vents.

    We are in Ontario Canada. Outside temperatures are currently in low/ mid 80s, attic is about 90 while ground floor (where thermostat is) is at 74.

    Finally my questions!

    What would you suggest as a good way of improving cooling in the attic bedroom?

    We are considering having contractor strip the ceiling (acoustic tiles) and end wall with view to improving insulation either by installing block foam insulation or spraying.

    Another consideration, would be to install a window or portable air conditioner just for this room (It is a guest room, so these would only be used when needed.

    Another idea would be to install a window fan and exhaust the hot air. We currently use an oscillating fan to try and mix hot air at peak of a-frame ceiling with cooler floor air. Because of furniture, this doesn't work well.

    At this point, I don't know whether I need a building contractor or HVAC help.

  2. #2
    Join Date
    Aug 2003
    Location
    Fort Worth, TX
    Posts
    11,348
    If you have any walls in this room exposed to the attic, and these walls are not insulated, or have exposed batts facing the attic...this is the best place to start working on the problem. Exposed batts need to be covered by drywall or foam sheathing. Non insulated walls should not be left that way.

    Also, if you can see underneath the floor of the room in the attic (between the joists that support the floor of the attic room and ceiling of the story below the attic), those gaps should be blocked (filled) to stop air movement underneath the floor.
    • Electricity makes refrigeration happen.
    • Refrigeration makes the HVAC psychrometric process happen.
    • HVAC pyschrometrics is what makes indoor human comfort happen...IF the ducts AND the building envelope cooperate.


    A building is NOT beautiful unless it is also comfortable.

  3. #3
    Join Date
    Aug 2011
    Location
    Kingston, Ontario
    Posts
    207
    Thanks for comments

    Quote Originally Posted by Shophound View Post
    If you have any walls in this room exposed to the attic, and these walls are not insulated, or have exposed batts facing the attic...this is the best place to start working on the problem. Exposed batts need to be covered by drywall or foam sheathing. Non insulated walls should not be left that way.
    There are wing walls about 4 ft high on each side that are exposed to the attic. They are 2x4 walls insulated with F/G batts and then covered on attic side with 1" foil backed polyisocyanurate foam. The ducts are in the wing wall cavities. They have 1" insulation, but are also buried in cellulose insulation - this extends about 1/2 way up the outside of the wing walls. Not much more we can do there. But we could add a whirly bird attic ventilator perhaps (only have one static type vent on each adjoining attic)

    Also, if you can see underneath the floor of the room in the attic (between the joists that support the floor of the attic room and ceiling of the story below the attic), those gaps should be blocked (filled) to stop air movement underneath the floor.
    The attic bedroom is directly above a lower bedroom. From what I recall, because of the framing and the blown in insulation there should be no way for air to flow from attics under floor.

    Did another check this morning. Cloudy day, outside temperature 78F. One attic temperature where air handler is (the ones adjacent to wing walls are hard to access) was 81.5F (it has a whirly bird). The house is at 74F and the attic bedroom was at close to 80F. This is a very good day. Usually much hotter up there when sun is out.

  4. #4
    Join Date
    Aug 2011
    Location
    Kingston, Ontario
    Posts
    207
    Quote Originally Posted by Freeagent View Post
    Did another check this morning. Cloudy day, outside temperature 78F. One attic temperature where air handler is (the ones adjacent to wing walls are hard to access) was 81.5F (it has a whirly bird). The house is at 74F and the attic bedroom was at close to 80F. This is a very good day. Usually much hotter up there when sun is out.
    Sun out this afternoon. One outdoor thermometer say 80F, other says 84F. Attic where air handler is - 102F (roof faces South and no shading). House still at 74F. Attic Bedroom 83F. Measured wall/ceiling temperatures 88-91F.

    Seems like with the attics getting that hot, it will be hard to get the bedroom cool. Maybe booster fans in registers?

  5. #5
    Join Date
    Nov 2006
    Location
    Athens, Ohio
    Posts
    1,817
    I suspect the thermostat is on the first or second floor. Hence it cannot sense the attic room temperature. I suggest you turn the blower "ON" so that it will continue to deliver air to all rooms, especially the attic bedroom, even between cooling cycles. You'll be amazed at the difference it will make in 24 hours.

    You should not overlook the other suggestions regarding improving insulation for the room.

  6. #6
    Join Date
    Jan 2008
    Posts
    2,031
    Mini-split would be perfect.
    "Hey Lama, hey, how about a little something, you know, for the effort." And he says, "there won't be any money, but when you die, on your deathbed, you will receive total consciousness." So I got that goin' for me, which is nice. - Carl Spackler

  7. #7
    Join Date
    Aug 2011
    Location
    Kingston, Ontario
    Posts
    207
    Quote Originally Posted by kdean1 View Post
    I suspect the thermostat is on the first or second floor. Hence it cannot sense the attic room temperature. I suggest you turn the blower "ON" so that it will continue to deliver air to all rooms, especially the attic bedroom, even between cooling cycles. You'll be amazed at the difference it will make in 24 hours.

    You should not overlook the other suggestions regarding improving insulation for the room.
    We have two temperature sensors which the thermostat averages. Both are on main floor where alll rooms are located except for attic bedroom. We could add a third sensor in the attic room, but then the main floor would likely get too cold.

    We have had the fan set to "circulate" - But reading the thermostat manual, I see that only circulates 35% of the time. There is another setting "On" and that should circulate 100% of the time. I havse now set it that way - Thanks for the tip.

    I am not discounting adding insulation. But it will require ceiling to be removed and quite a bit of other work. We may very well get it done sooner than later.

    PS: 2old2rock - Mini-split? We don't need heating in the attic room (heat gets there anyway!). Just cooling, so if our central system won't do job, fall back could be a small A/C. Maybe a portable type would be better than window type so we don't have to remove in winter? Mini-split is a bit expensive for one small room.

  8. #8
    Join Date
    Jul 2011
    Location
    Nanaimo,BC, Canada!
    Posts
    346
    You'd be amazed with the results of running your air handler fan continuously .. I recommend it to all my customers.. Residential and commercial ..

  9. #9
    Join Date
    Aug 2011
    Location
    Kingston, Ontario
    Posts
    207
    We now have it that way. Not much improvement in temperature, but feels better due to air movement. Going to try different register that we already have with more open area to try and direct air more upwards so as to get better mixing - currently it is cool down around my ankles

  10. #10
    Join Date
    May 2004
    Location
    south louisiana
    Posts
    3,189
    http://www.southface.org/default-int...gkeypoints.pdf

    page 5 details kneewall sealing & detail work to seal between joists
    as per Shophound's post.

    insulation slows air movement, it doesn't stop it.
    heat gain from attic @ kneewalls is what makes this
    room difficult to condition.

    best of luck.
    The cure of the part should not be attempted without the cure of the whole. ~Plato

  11. #11
    Join Date
    Aug 2010
    Location
    West Monroe, LA
    Posts
    1,535
    Quote Originally Posted by energy_rater_La View Post
    http://www.southface.org/default-int...gkeypoints.pdf

    page 5 details kneewall sealing & detail work to seal between joists
    as per Shophound's post.

    insulation slows air movement, it doesn't stop it.
    heat gain from attic @ kneewalls is what makes this
    room difficult to condition.

    best of luck.
    I agree with energyraterla. Knee walls are some of the most overlooked walls in the home. Contractors/customers often pay for blown in insulation in exterior walls and ceiling but only get the knee walls batted which makes no sense.

    Knee walls are the hottest exterior walls as they connect condition space to the attic which exceeds outdoor temps that regular exterior walls receive. It's no own common for these walls to see 125-150 degrees in the dead of summer or even higher and the only thing stopping the heat from transferring from attic to condition space is often only a R-11-19 batt and Sheetrock. While this is common practice for whatever reason it is wrong in my opion.

    This walls should be installed to the Max with the best insualtion just like the rest of the home. Foam insualtion, blown in insualtion with netting or batts (in the case if blown in or batted insulation I would suggest strofoam backing, Sheetrock or another product to offer more insulating factor and ensure the insualtion stays in place.

    Of course you could install a window unit, ptac or mini split unit just to service that room but if the knee walls are causing the probelms you should be able to get that addressesd at a lower cost then the ones I listed.

    As I read the original poster responses before posting I see you have done just about everything to insulate the walls that can be done. So the problem might be one system doing two floors or placement of the t-stat? Mini split might best option for this room?

  12. #12
    Join Date
    Aug 2011
    Location
    Kingston, Ontario
    Posts
    207
    Of course you could install a window unit, ptac or mini split unit just to service that room but if the knee walls are causing the probelms you should be able to get that addressesd at a lower cost then the ones I listed.
    Thanks for the replies.

    The knee walls are already quite well insulated. Only additional insulation we could add would be by adding 1" foam board on inside of walls (which could be done). Up to 50% height, knee walls have r11 +R5 plus about a foot or more of cellulose. Above that (about 18" x 30ft altogether it is R11 +R5.

    Sloped ceiling roof insulation is an unknown - It has batts in between 2x6 timbers. But condition unknown. We were thinking of stripping ceiling tiles and seeing what gives, then drywall the ceiling and walls (currently panelboard covered with wallpaper). Maybe spray insulate or add solid foam blocks if insulation is needed?

    Seeing this room is only used occasionally for guests, perhaps we should just add cooling or perhaps vent the room from high up or through window, just when occupied? Window does not lend itself to A/C (horizontal sliders). So maybe a portable? Less expensive than a mini-split!

  13. #13
    Join Date
    Aug 2011
    Location
    Kingston, Ontario
    Posts
    207
    Just a follow up observation.

    Today in Ontario, Canada, we have a very hot day for us. Low 90s. With tstat set at 74F, the a/c is running more often.

    When outdoor temperature was low 80s, a/c did not run as often and temperature in attic room was about 7degrees high than lower level (about 81F vs 74F). Today with 92F outdoors, attic room is at 77F. In other words cooler than it would be on a cooler day outdoors.

    Reason, no doubt, is because A/C is running more often and more cold air is getting to attic room. Attic heats up more quickly than lower floor, so on cooler days it just gets hotter and hotter up there until air flow resumes.

    In reading air handler manual, cfm can be set as follows (+/- 10% at each tap):

    Heating 1200 or 1000
    Cooling 1200 or 1000 or 800
    Blower only 600, 500, 400 or 350.

    I know we have the heating cfm at 1000 (to limit noise). Not sure about cooling, but there is less noise and I think tech said 800cfm. Blower on recirc has very low noise, not sure, but perhaps 400cfm.

    The system is a Mitsubishi Zuba rated at just over 3 tons (38k btu/hr for heating)

    Would it make sense to have the blower bumped up to 600CFM? (It is a job for tech because adjustment is by jumpers on internal circuit board). Or perhaps in interim add register boosters to the two inlets?

Page 1 of 2 12 LastLast

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
Comfortech Show Promo Image

Related Forums

Plumbing Talks | Contractor Magazine
Forums | Electrical Construction & Maintenance (EC&M) Magazine
Comfortech365 Virtual Event