Building with the Sun in Mind

[sansei]

One basic design consideration when building to take advantage of the sun is the orientation of the home relative to the way the sun traverses the sky. Everyone of knows the sun rises in the East and sets in the West. The path of the sun also moves between North and South in the transition between Winter and Summer Solstice although the Island's proximity to the Equator reduces the effect.

The orientation of the house pre-determines many subsequent design decisions like roof overhang and glazing. Orienting the house on a North-South/East-West grid allows simple roof mounted collectors to maximize collection without trackers or tilting the collectors at an angle that can catch the wind in a storm. Roof mounting when it can be done is nice because it does not take up any extra real estate. The collectors mounted flat to the roof minimizes the impact to the aesthetics of the design, uses cheaper mounts and would not affect catchment as long as the materials used are non-reactive.

Orienting the home according the compass also works for passive solar. An example would be my present home in California that I oriented East-West. I have 7 six foot sliders on the South face. The sliders let the sun warm the house in the Winter when the sun angle is low to the south but is shaded by the roof and deck overhang during the hot summer when the sun is to the North.

One of the unique aspects of living on an island is that the geography is described in terms of Mauka and Makai. The lots generally run Mauka-Makai to follow the slope of the land which of course means the house may have to be rotated at an angle to follow solar design pricipals. In HPP for instance, a home has to be rotated nearly 45 degrees from the lot line which is further challenged by the narrow lots and the required set backs. The only sub-division that more or less follows a N-S/E-W orientation seems to be Leilani.

A Mauka-Makai side story: Having grown up in HI, I was completely blown away when I first moved to LA and I had to drive on the freeways. Not only were the freeways on a scale way beyond anything in the islands, but directions based on N-S/E-W was completely foreign. It took me a while to condition myself to look up in the sky at the location of the sun relative to the time on my wrist watch to determine direction instead of getting frustrated.

I would be interested in hearing other thoughts on the topic. Of course not being able to orient collectors on compass grid is not an excuse for not doing solar. I am just a nerd engineer trying to live a green life style but I am always looking to engineer a way to optimize the return on investment.

There is a really neat calculator provided by the US Naval Observatory that creates a table of Sun Altitude and Azimuth through the day at the location of your choice. It is easy to calculate things the roof/deck overhang and the shade effect of a tree using the table and a CAD program. The web page is here:
http://aa.usno.navy.mil/data/docs/AltAz.html

Life without challenges would be boring.


Larry

Edited by - sansei on 08/24/2007 06:39:37

Edited by - sansei on 08/24/2007 06:40:58

[Hotzcatz]

Don't forget to also take the tradewinds into consideration when designing a house in Puna. With the cost of our electricity and/or the size of the system required should one choose to run A/C on a photovoltaic system, it is a lot less expensive to have the tradewinds cool your house instead of electrical machinery.

Some old style houses were up on post and pier and had ventilation grids in the bottom of closets with louvered doors on the closets as well. High ceilings (min. 9' instead of the "standard" 8') help keep the hot air up away from folks and allow for a "cooler" house. A ten foot ceiling would be good, it also adds to the spaciousness feeling inside the house. You can build a smaller house (less expense and upkeep with more time to go to the beach) that "feels" big if the ceilings are high.

Putting a huge lanai all the way around the house shades the sides of the house as well as gives you a huge "outdoor" living space. A few sections of clear roofing or sola-tubes would allow lighting in without using additional electricity, too. Some sort of closeable louvers or drape would be good, though in case of too much sun.

[Daniel]

Aloha Larry,

I also plan on building the most environmentally friendly house that I can. It seems to me that the benefits of pointing your house south don't really apply to hawaii. Except like you said if you were to put PVs or hot water heaters up there. I think you would find more benefits in orienting your house with the trade winds and finding ways to cool your home naturally. However you can design your house to do both. you can have a large roof area pointing due south with windows and vents faceing the trade winds. There really isn't a need to heat a house here unless you live in volcano...and if you build it right, you shouldn't need to have AC either. There are many ways to cool your house without AC. Build with the sun in mind, but try to keep its heat out of your house while letting its light and energy in.

A hui hou,

Daniel R Diamond

[sansei]

I am advocating being aware of the way the will interact with your home so you can design to take advantage of it or compensate for its efffects. It is after all the biggest, by far, energy source in our solar system.

There are things that you can do during the design/build phase that can make the home more comfortable without adding a great deal of cost. One example is to use foil faced insulation or sheathing on the south and west facing walls. Knowing which walls will have the hot sun beating on it allows you to be selective instead of brute forcing it on all walls.

I look at a lanai on its own merits of combining indoor and outdoor living space. I also adds to roof sf for catchment. Best of all it is not counted as indoor sf for tax purposes.

I prefer using roof overhang selectively because in cuts off light from entering glazing. I like the added openess when I can look out a big glass window without the sky being cut off by a roof or deck overhang.

One other feature I like is celestory windows. My present home has a 8/12 pitch on half and 4/12 on the other half. Where they join is a wall that I filled with awning windows (facing north for heat control). The windows let lots of natural light in. The top of the 8/12 roof section is the high point in the house so the windows naturally exhaust hot air from the house with an extra boost from ceiling fans if needed.


Larry

[Kapohocat]

quote:

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..I look at a lanai on its own merits of combining indoor and outdoor living space. I also adds to roof sf for catchment. Best of all it is not counted as indoor sf for tax purposes...
Larry

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It is taxed though as is an accessory space is taxed (garages, workshops, etc).

Catherine Dumond
Blue Water Project Management
808 217-7578
http://bluewaterpm.125mb.com/index.html
"We help make building your dream home a reality"

[emorata]

Can someone advise how the trade winds blow typically through hpp/orchidland subdivisions and how you would orient the house to take in the cool breezes

thanks in advance

noel

[hpp4me]

Also, if you have lots of windows on all four sides of the house, aren't you covered regardless of how the house is situated on the lot?

[Daniel]

A little money saving tip:

Instead of using mylar that has bubble wrap or insulation glued to it, just use plain mylar. you can buy it in big rolls and staple in right to your the underside of your roof using stainless steel staples. It is just as effective and a lot less expensive. Some people even put it on under the roofing or under the tar paper.

Daniel R Diamond

Edited by - daniel on 08/27/2007 14:27:28

[Kelena]

Agree. The sun should be taken into account. The sun can overpower any tradewind. If you have windows that receive the full blast of the Summer Sun, no tradewind will help. It is important to orient correctly and to have a sufficient overhang to protect the house from sun and rain.

[Guest]

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