The ABC's of the PHPP - Part 9 Summer Time and the Living is Easy
Tuesday, February 21, 2012 at 12:48AM 
I grew up in the South and when I think of summer, I remember those summers because as the song says, the living was easy. It had to be – it was too darn hot to put a lot of effort into much of anything. When I was a kid it was a rare thing to find a family with air conditioning in their home. Riding in a car meant rolling down the window to keep cool. Going to the movies was a treat to beat the heat because they did have AC, and of course a run through the sprinkler cooled off many a kid. For me nothing was better than a good book, a shady spot, and some iced tea.
I now live in the Pacific Northwest and there are a few days maybe a week or so when the heat can be a real problem to contend with, but nothing like the summers I spent in the South. But even here where we are lucky to have such a great climate, we have to worry about overheating in the summer even in a Passive House. Oh, sure it is not much, but the designers need to make sure where ever their project is located, they consider the circumstances that are specific to the summer months and provide for the additional heat blocking measures that may be necessary.
Because the PHPP looks at the specific details of your project’s location, orientation, design specifics, and usage characteristics it is able to tell you when overheating can be anticipated. In this manner you have the opportunity to model your project for comfort all year round and provide the extra planning that will keep you comfortable even when the temperatures soar.
I was in an A-frame structure about a year ago and it was quite comfortable outside, but after a few minutes inside I was practically melting in sweat. The design had the typical floor to ceiling wall of windows facing the most gorgeous southern view. I imagine that at the time those structures were popular that many a homeowner was shocked by the amount of temperature extremes those buildings could produce. If they had the PHPP to design those buildings then I bet that many would have been designed differently – but that type of design is still possiblefor a Passive House in the right location with the proper planning. Take a look at the first certified Passive House in New York and you will see what I mean. http://www.hudsonpassiveproject.com/
So, when entering your project into the PHPP, just what do we need to be aware of with the Summer worksheet? This is where you can let the PHPP know if you are going to be opening windows manually for cooling, or have some kind of automatic ventilation system triggered by the indoor temperature. Be sure to plan any mechanical system appropriately - the PHPP manual makes special note that “If the ventilation system will be operated at an increased air change rate in the summer, it must be dimensioned for this purpose at the initial design phase. Doubling the rate of air flow while leaving the air duct network unaltered increases power consumption by four to eight times, and adds waste heat for the fan motors to the air.” [1]
The Shading Summer worksheet of the PHPP is where you will enter additional shading that is specific to the summer months. You will see that the shading factors that you already filled in on the Shading Worksheet have been brought forward, but now you can add to them for additional shading, such as from deciduous trees that are only shading the structure during part of the year. There is also a column for temporary shading structures where you can enter a shading reduction factor – the higher the number the less shading. The PHPP manual has a chart with some reduction factors for low-e triple glazed windows. Other reduction factors can be obtained from window manufacturers, or calculated per DIN EN 13363.
Next up – Summer Ventilation
[1] Passive House Planning Package 2007, pg 115.
Reader Comments (1)
In Summer,there is very hot all around & i am also discover the cool place as you.Just like the theaters,a shadow of tree & any where in cool place.I like your article.Thanks for the post.