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  1. #1
    hugodrax Guest
    I put up my turbine vents that spin and do no require any power etc.. do they actually do anything regarding dropping the heatload? what is the advantage of them. I decided to give them a shot after being tired of seeing them in storage for so long.

  2. #2
    Join Date
    Aug 2003
    Location
    Fort Worth, TX
    Posts
    11,370
    If you're speaking of the wind driven turbines that are supposed to help ventilate an attic in summer, they work if the rest of the attic's ventilation system is set up correctly.

    To adequately vent an attic in hot weather, air must enter at the soffits and be expelled at or near the ridge or peak. This is the natural flow of heat; as it rises it will draw in relatively cooler air from under the soffits and expel it through ridge vents, gable end vents, turbines, or other means.

    I recently went to a house that had the underside of the roof over the attic insulated with spray-on foam. Rather than allowing the heat to penetrate the roof decking into the attic, the insulation essentially made the attic a conditioned space. On the weather side of the roof deck, special provisons were made to allow air movement underneath the shingles so they would not cook in the Texas sun. It was in the low nineties that day and the attic felt comfortable compared to most other attics on a similar day.
    • 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
    hugodrax Guest
    I have soffit vents across both sides of the home and the 3 turbines (passive) are at the peak edge of the roof, but what is confusing is some places indicate it does nothing and some indicate it helps. I live in southflorida so maybe it helps who knows.

  4. #4
    Join Date
    Aug 2003
    Location
    Fort Worth, TX
    Posts
    11,370
    Originally posted by hugodrax
    I have soffit vents across both sides of the home and the 3 turbines (passive) are at the peak edge of the roof, but what is confusing is some places indicate it does nothing and some indicate it helps. I live in southflorida so maybe it helps who knows.
    If the turbines are the only exit for the heat rising from the attic and air that is drawn in through the soffits, the turbines are far better than no exit at all for the heat.

    The key about soffit venting is that they need a non obstructed path of air entry into the attic. Often, insulation is shoved right up to the point where the wall top plate and roof trusses meet, leaving little to no room for air to enter and ventilate the attic. There are foam channels available to place over the insulation at this point to allow both air to enter and insulation to be in place right up to the wall top plate.

    You might find this article of interest:

    http://www.buildingscience.com/topten/south.htm

    His main objection to ventilating attics in a humid climate appear to be based on the notion that moisture in the attic will condense on the cool surfaces of ductwork and the topside of ceiling drywall. Sure, if those surfaces ever reach the dewpoint of the air. He also contends the main issue with heat in an attic is radiant heat, which can't be ventilated. It's true, radiant heat will pass through the air without warming it and will only warm a surface that it strikes. This would appear to bolster a call for a radiant barrier, either as incorporated on the underside of roof decking or attached to the underside of the roof rafters.

    My limited experience with radiant barriers has been positive when they're installed correctly. There's a roof decking product called "Tech Shield" that's beginning to show up in new construction around here. I once visited two houses under construction side by side on a hot afternoon. One attic used Tech Shield and the other did not. Both houses were enclosed but no drywall was installed yet. The attic of the Tech Shield house was much cooler than the one next door.
    I would like to research the radiant barrier issue further, as there are aftermarket options for those of us who don't have radiant barrier impregnated roof decking. My experience in most of the homes I've lived in is that long after the sun has gone down, I can still feel radiant heat entering the house, even with adequate insulation and ventilation of the attic. It can make one feel warm even when the space temperature and humidity seem under control.

    I think the best approach is to keep as much heat as possible out of the attic from the start. Personally I intend to build a house someday with NO attic. It will instead use a highly insulated roof with a standing seam metal cladding instead of shingles. Radiant barrier underneath the decking. All a/c ductwork in the conditioned space. Low E double pane warm edge technology windows. Metal framing for studs, joists, and rafters, or one of the emerging insulated concrete block technologies coming onto the market for the walls. Result? A house that's hard for termites to eat, one that's more fire and wind resistant (important in Tornado Alley and Downburst Drive), and one that's easy to heat and cool. It won't be a big house, it'll be a quality house that's both architecturally appealing and is pleasant to live in year round.

    • 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.

  5. #5
    Join Date
    Aug 2004
    Location
    North Richland Hills, Texas
    Posts
    14,915
    IMO, putting composition shingles on a roof in Texas should be a capital offense.


    Shophound,
    We both have similar plans when it comes to building a house. I'm looking closely at the autoclaved aerated concrete(AAC) products. The systems I have been looking at also have AAC roof sections available. I'm thinking a nice lightly sloped roof made of AAC, with some kind of REALLY white roofing system, would do a really good job of keeping the heat out in general and would prevent peaks in loads.

    I'm exploring the idea of using a drop grid cieling system so everything above the cieling has easy access. I'm also looking at the KaRo radient cooling/heating system using thier radient panels in the cieling grid. Dehumidification/humidification, fresh air and air movement would be handled by a system that is independant of the sensable cooling and heating system.



    [Edited by mark beiser on 04-09-2005 at 08:12 PM]
    If more government is the answer, then it's a really stupid question.

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