Adding a deck structure to break the wind
I have a 1-story ranch in zone 5 , Colorado mountains, that sits on a full basement with a walkout on the end under the great room. This end of the house faces along a valley up which we get a lot of wind. From October through March there is 30-50 mph wind a lot of the time hitting the end of the house, finding every air seal leak, pressurizing the walls and ceiling cavities, and stripping off the boundary layer around the house. When the wind blows the heating load goes up very noticeably. I need to replace the deck at that end of the house and I thought that perhaps I could incorporate some kind of wind screen/ramada structure into the new deck that would blunt the direct wind pressure on the house and/or deflect the wind around the sides. Would anyone know of a reference for design of such?
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I've designed a few windscreens in NM, and I think a few outside pictures would help visualize your situation.
Armando, I have added two pictures - one showing the end of the house with the deck to be replaced, and a 2nd showing the fetch of the wind down the valley. No trees to shelter the house. My idea was to frame the new deck with strong two-story vertical posts and add a ramada roof and some sort of vertical deflector inserts to create eddies out at the front of the deck. I want the structure to spill the wind but drain it of energy across the face of the house. I don't want to interfere with the view any more than necessary. I just don't have any design reference for such a thing.
You need to find the right balance for wind screening and visibility. Since I don’t know how your house was structurally designed, I would venture to say that extending the roof to form a covered-screen porch maybe a good option for the upstairs, and enclosing the bottom porch as well.
You could use Metro Screenworks’ Super Screen. It comes in 10’x100’ rolls, a heavy-duty screen, which is durable against wind, hail, pets and wild critters, but allows you to maintain good visibility. They have two mesh sizes, which you could use the standard mesh (17x14) for above the handrail, and a tiny mesh (17x20) for bellow the handrail, and maybe on a section or two on the sides to block more wind, depending on views.
Since most strong porches are framed in four foot sections, maybe the first section on the edges, could be solid framing.... or not!
If that's not enough wind blocking, you could build solid rails on both porches, but that would block some of the views.
WMF,
One of the problems is that while the wind is creating positive pressure on the face of the building and driving air into the house, the same wind is also creating negative pressure on the opposite side pulling air out of the building. I'm not sure you can do much to stop those two air-movements with a wind-break, which are typically used to create usable decks and outdoor spaces, not was a substitute for air-sealing.
If you’re really lucky, the “point” of your house points into the wind. I’m not sure if that’s the case here. A real wind break for 50 MPH winds is going to have to deal with around 20ish pounds per square foot of loading, so you’d basically have to build a sideways floor. You can reduce that load by keeping the wind break oriented at angles to the wind so that you aren’t making a big flat wall perpendicular to the wind.
I’d look into using clear polycarbonate panels, probably 1/4” thick which is usually the best price/strength value. Frame it using snow load tables for roofs, but using that 20 pounds per square foot number from the wind force, which should get you close in terms of load handling ability. Orient the structure so that it’s a wedge pointed into the prevailing wind.
That’s my idea anyway, but I’d recommend having a structural engineer do a design review of whatever you end up choosing to do. The risk you have is a piece of the wind break tearing off in a gust and smashing into your house, possibly coming through a window. You want your structure to be safe.
You may find it’s easier to just add additional exterior rigid foam on the side(s) of the house facing into the wind and doing a very good job of air sealing. The lee side of the house isn’t as important in this case.
Bill
Thank you for your comments and information. I will continue to research this and maybe post if I manage to develop something useful. The deck/ramada will need to be designed by a structural engineer anyway for several reasons, so the wind pressure will be taken into account.