hvac for foam insul conditioned attic - Page 2
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  1. #14
    Join Date
    Nov 2004
    Posts
    2,927

    Re: summer costs

    Originally posted by señord
    Is this representative of longer cooling
    months time vs heating time? i understand your
    explanation, but I can forsee more usage
    in summer or warmer months vs cold winter
    needs..
    thanks, Sr. D
    that depends on you
    if you want 68 degree with 50% RH in the summer you will pay more than if you want 72 degree 50% RH

    same concept applies in the winter

    the local climate is sometime mild and then sometimes harsh.
    the summers are always hot and muggy and the winters sometimes are "severe" about every other year

    there is a long transitional season almost every fall and spring.

    The weather is unpredictable.

  2. #15
    Join Date
    Nov 2004
    Posts
    2,927
    Tell your builder you want a Goodman heatpump

    [Edited by jacob perkins on 02-03-2006 at 11:51 PM]

  3. #16
    Join Date
    Jan 2004
    Location
    Location: Tulsa Oklahoma
    Posts
    222
    We recently installed a condensing gas furnace and a 14 s.e.e.r. condensing unit on a log home in Claremore Oklahoma.
    The homeowner had the Icyene foam sprayed on the attic rafters
    and it works great. You need to install an E.R.V. unit in the
    house to introduce air into the system with these tight home
    insulation packages. Be sure to get a quality contractor that
    is familiar with the foam house envelope requirements. You will be very impressed with the way the house performs. If you
    are in a total electric area only then use the heat pump, otherwise a 2 stage gas furnace would probably make you happier. Good Luck with the new house.
    Whoa Maynard - that's not how it works.

  4. #17
    Join Date
    Feb 2003
    Location
    Huntsville,AL
    Posts
    4,125
    where in OK? seems to me that this is a good size state -

    ask builder what the local normal design conditions are for 99%, for 97% --

    on slab?
    bsmt is my first choice, then crawl in which one can sit, slab only if I am forced!

    consider having a SafeRoom -- against tornados --

    what I am stating, is that I would not want a potential source for water leaks in my attic --

    BTW, here, of late, we seem to have SHORT fall & spring seasons! & so far, very mild winter this yr.
    harvest rainwater,make SHADE,R75/50/30= roof/wall/floor, use HVAC mastic,caulk all wall seams!

  5. #18
    Join Date
    Jan 2006
    Posts
    25

    icynene

    coolmist and cem-base- The home will be in soutwest
    okcity, near Moore. We are used to gas furnace, but
    only have limited knowledge about heat pump as of late.
    Dealing with humidity is a new task for us, as we
    are in dry heat in calif.

    I saw a whole system online by Lennox that shows the
    erv, hepa filtration, etc, etc, and I am thinking of
    asking the builder to use this vs luxaire equip. I
    will ask the builder if he has 100% confidence in
    installers, and if I do not like my answer (ex. How many installs have they done with similar envelope, etc)
    then I guess I will have to start making long
    distance calls myself. I did talk to one company's
    sales/serv guy who said that they had done this system
    (not sure how many times he said) before. Last, I can
    check with the better business bureau? otherwise, A
    post from here in the area could pm me about install
    recommendations? Señor D

  6. #19
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
    Posts
    6,232
    Fresh air ventilation is must for a well built home in any climate. I have never monitored a home with fresh air ventilation with any kind of a/c that was able to maintain <50%RH throughout the home, during wet 60^F-75^F weather and typical occupants. Some infer that humidity control is assured with the new complex a/cs. Get it in writing from the mfg and monitor %RH during low/no load conditions. The new complex systems are better, but are unable to remove the 100 lbs. of moisture/day with low/no cooling loads. we fix 100s of the newest systems of all brands every year by adding dehumidification. If there is enough interest, we could setup live web-based temp/%RH monitoring in any home to observe humidity control with different systems. This info would be available to all posters. This could remove some of the puffery from the claims. Fresh air and %RH is critical for indoor air quailty. Also being able to maintain %RH without having to operate a large a/c system to provide %RH control when the home is unoccupied saves enormous amounts of eneryg. TB

  7. #20
    Join Date
    Jan 2006
    Posts
    25

    conditioned attic ventilation

    I am so impressed with the numerous replies. Here's one more question. Should there be any opening to the main floor of living space to the foam sealed attic space? Or is the attic access and various wall cavities air supply going to keep neg pressure, etc. from developing? I also wonder about those air vents above the bedrooms I saw in a model home once to keep circulation and consistent temps
    thru-out the home. Are these necessary, as in my current
    home the air passes beneath the door when the door is closed? I just couldn't help but think "unproven sales gimmick". chime in if you like...

  8. #21
    Join Date
    Aug 2003
    Posts
    626
    If you want comfort, low utility bills, good IAQ, structural durability, you must build the house as a "system". One thing effects the other. An example of this is what you are doing to your new home. By using foam insulation, you will make the home more energy efficient and comfortable, will lower the size of your HVAC unit, and create a demand for mechanical ventilation. The best way to do this is to start at the planning stages and do the details right. A good source for this is http://www.buildingscience.com in the Building America section. Study this and you will be happy every month you are in the home and at resale time.

  9. #22
    Join Date
    Mar 2004
    Posts
    1,042
    I'm a firm believer in putting a return duct in every bedroom (I think this is what you're asking about, senord?). The only time this isn't necessary is if you never close the bedroom door.

    If you use them, the temperature in the room will be the same if the door is open or closed. With the door-cuts, you typically find that a bedroom over- or under-conditions when the door is closed for a long time. If the extra ductwork is going to be a problem, you can also consider a "jump duct" which is just a freestanding duct that allows air flow to return from the bedroom to the central return even when the door is closed. This could just be a short flex duct (best for acoustic control) connected between two small return grilles; one in the bedroom and one in the hallway outside the door, no direct connection to the rest of the system. Some people have also used an interior wall cavity for this purpose, but I might worry about sound transmission with that setup.

    As for summer versus winter usage, you'd be surprised. While each season may be of equal length, think about room temperature and compare it with outdoor temperatures in each season. During the summer, the temperature may hit 95 outside in the late afternoon. In the morning, though, it's probably only in the 80s, and it may get down into the 70s overnight. During the summer, you probably are using air conditioning to keep the temperature to a maximum of 75. So the peak temperature differential you're trying to maintain between inside and outside is 20 degrees, and over a typical 24-hour period in the summer the average difference is probably less than 15 degrees. During the winter, you probably use heat to keep the temperature to a minimum of 70. During that time, the temperature may get down to 15 degrees occasionally; most nights and mornings are probably around 30 degrees. During the day, you may make it up to 60 degrees sometimes in the afternoon for a few hours. So during the winter, in an ideal case you're trying to only maintain a 10 degree difference, but the typical is probably more like 25 degrees, and sometimes the difference may be more like 45 degrees. Overall the average temperature differential you need is much greater during heating season than during cooling season.

    So if you look at overall energy consumption, the typical American home in a moderate climate uses 2-3 times more energy for heating than for cooling. That doesn't necessarily mean that the same relationship is present for heating cost versus cooling cost, though.

  10. #23
    Join Date
    Nov 2004
    Posts
    2,927

    Re: great info

    Originally posted by señord
    heat pump may present savings, but I am
    still not convinced on significant vs. just a little. I feel that with the relatively smal size of home, and that we are home mostly evenings, weekends, holidays, and summer, I can not justify additional cost.
    I think significant is the best descriptive term. The cost to heat will be 2-3 times less than electric,and probably about the same compared gas. The payback will be seen in a few years at most...

    As for insulation :
    The thing to consider is your personal preferences. Do you want a hermeticaly sealed building envelope or do you prefer to breath the fresh outdoor air occasionally? The way the wind blows in Ok.,I'm sure there is clean fresh air most the time.That is something you will have to research.You might be downwind of the stockyards or something.
    Tight construction is good for people who need it,and a waste fot people who dont.

  11. #24
    Join Date
    Aug 2003
    Posts
    626
    Jacob Perkins---The statement you made about "some people need hermetically sealed tight homes and some don't" reflects your basic lack of knowledge on how homes operate. Depending on temp. difference or wind to ventilate a home through it's holes is a poor way of ventilation and wastes energy. The only proper way to ventilate a home is to build it as tight as economically possible and mechanically ventilate it. When any new home can be mechanically ventilated for under $300.00 there is no excuse not to.

  12. #25
    Join Date
    Nov 2004
    Posts
    2,927

    Re: Re: great info

    Originally posted by jacob perkins
    [The thing to consider is your personal preferences. Do you want a hermeticaly sealed building envelope or do you prefer to breath the fresh outdoor air occasionally? The way the wind blows in Ok.,I'm sure there is clean fresh air most the time.That is something you will have to research.You might be downwind of the stockyards or something.
    Tight construction is good for people who need it,and a waste fot people who dont.

    well I am glad to see you are trying to help the poster with his query into energy costs as it relates to a residence in Oklahoma ,but...my answere was based on cost analysis,with the objective of saving dollars.After all,that is what he seemed to be asking.


    How you came to your conclusions about what I said is a mystery though...as is the price you list for mechanical ventilation. So,why dont you make your sales pitch...I mean ,explain the proper ways in more detail. I am sure to benefit from your experience and wisdom







  13. #26
    Join Date
    Aug 2003
    Posts
    626
    I am sure you could benefit from my experience. I recommend you do research at www buildingscience.com . They go into why every home should be built tight and mechanically ventilated and the different methods to do so. I hope you will come away enlightened.

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