Prevailing Winds and Windows

Once the initial plans for a house are firming up and its time to decide on window details, consider the prevailing winds. You may know your site well enough to know what direction the winds tend to come from. To be sure about this you can research prevailing winds for a spot near your home site using tools such as Wind History. Given your house design style, you may have options for sash windows, casement or awning. We are currently advising a high end modern being constructed near Soloman's Island on a promontory along a river feeding the Chesapeake Bay. Here the winds tend to come from the NW or the SW during the warmer months and we know that the windows/doors will not be open during the cold half of the year. We are also designing homes for Davis Riverwalk in downtown Davis WV - a mountain sports town at 3200ft elevation. This latter site tends to have many homes with no AC at all due to the temps being on average 10 degrees cooler than the DC area. However, the house design has a huge impact on whether the house is comfortable without AC through the warm months and in particular during the afternoon. Good window placement and type can extend the period when the occupant can skip AC or heat completely. Casement or double hung windows tend to allow a direct breeze to enter the house while awning windows tend to ventilate without much of a breeze. Casement windows open outward to the left or the right and should be specified to 'scoop' the air from the prevailing wind direction. Awning windows with electronic controls can be used up high to assist with chimney-effect ventilation as warm air rises in the house, exiting the high awning windows while cooler air enters at lower points in the structure. Fixed windows have a role here as well. Most houses have way too many windows that open in comparison to the actual use. Consider what ventilation is needed and then consider fixed windows otherwise. The advantage of fixed windows at ground levels is security. An advantage in general is better R value due to zero air leakage. And an advantage in some sites is noise. Davis Riverwalk is located right in town and some houses will be within 200 feet of main street. For that reason we will lean toward fixed windows on this (north facing) side of the Riverwalk homes. Since we are staggering house sites along the south side of the Blackwater River, we will look for opportunities to scoop in the winds that tend to come from the west by southwest and pass them through the house. We will look to 'chimney' air from the first floor to the second floor by having high ventilation windows on the second floor controlled by electronic openers. Cooler air blowing into the west facing windows will allow warmer air in the structure to rise up and vent out the high windows. Note that the same can be accomplished with electronic skylights but we will avoid opening skylights in this extreme weather mountain climate. In the Solomon's Island modern under construction now, we will focus our cross-breeze goals with our bets on the frequent west-to-east winds and we will use the north and south walls for passive awning windows, primarily up high. Where we have - for example - rows of identical windows, we won't have every one of them be opening windows. That creates clutter and unnecessary micro air leaks. We instead choose windows that will get the job done for those periods when the HVAC will not be used. At Solomon's, the house will primarily be conditioned, summer and winter, with users going in and out of the house frequently in the warm months, and the occasional period of neutral weather being our time to use the window ventilation. In Davis, we expect a much larger period of the year to not require much in the way of conditioning, so ventilation options are critical. This article does not address solar gain design considerations but, assuming these have been addressed, a good window/door plan will really help. http://windhistory.com/station.html?KNHK