7.18.2013

Design your house to keep it's COOL

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Designing Houses That Keep Their Cool

Follow these strategies to reduce the need for air conditioning

Posted on Jul 4 2013 by Alex Wilson
Summer is here, with a pattern of hot weather and (in our part of the country) high humidity. We can be glad in Vermont that we’re not dealing with temperatures approaching 120°F, as are Phoenix and Las Vegas. (Death Valley was predicted to hit 130°F the other day, just four degrees shy of the highest temperature ever recorded on earth — 100 years ago.)
Most new homes in Vermont today are being built with central air conditioning, and in much of the rest of the country, one wouldn’t consider a house without it. I’m not going to suggest that we should skip air conditioning systems with new houses (particularly with global warming), but through good design and smart operation of homes, we should at least be able to minimize the use of that equipment.
So, here are my top-10 strategies for home design to minimize air conditioning needs. Some apply only to new construction, others to renovations as well. They are not ranked by priority.



1. If you’re building a new house, orient the house wisely

If the site permits, the house should be oriented so that more of the windows face south than either east or west. During the summer months, far more sunlight enters a house through east- or west-facing windows than through south- or north-facing windows.
It may also be possible to orient the house to benefit from summer breezes.

2. Shade windows

South-facing windows can effectively be shaded with fixed overhangs, because in the summer the sun is much higher in the sky than in the winter — when that sunlight is beneficial for heating. With fixed overhangs, overheating in the fall months may still be a concern — because by then the sun is lower in the sky, while the outdoor temperatures may still be fairly high.
On east and west windows, fixed overhangs do not work well for shading, because the sun’s path through the sky is fairly low as it rises and falls during the day. For these orientations, vertical louvers, exterior roller screens, operable awnings, and plantings can provide effective shading.
In general, shading windows on the exterior is better than using interior blinds, as it keeps out more unwanted heat.

3. Tune window glazing by orientation

With or without shading, we can control unwanted solar gain fairly well by installing windows with different types of glass on the different orientations.
On the south side, glass with a high solar heat gain coefficient (SHGC) makes sense to bring in significant solar heat during the heating season, while on the east and west, low-SHGC glass makes more sense.
In most applications, look for SHGC values of 0.3 or lower for east and west orientations, while SHGCs over 0.5 (or even 0.6) usually make more sense for the south if passive solar heat is desired in the winter.

4. Insulate the house well

Unwanted heat gain enters a house not only through windows, but also through the walls and roof of a house. Installing lots of insulation in the building envelope will go a long way toward minimizing unwanted heat gain.
In a northern climate, R-40 in the walls and R-50 or more in the ceiling or roof makes sense. The house should also be airtight, so that when you want to close up the house during the day to keep heat out, you can do so.

5. Provide a reflective roof

A light-colored, reflective roof may help to keep unwanted heat out of your house. The best such roof should not only be reflective, but also have high emissivity. (A bright, galvanized-metal roof is quite reflective, but it also has low emissivity, so it can introduce a lot of unwanted heat.) Look for roof materials certified by the Cool Roof Rating Council or the Energy Star Roof program.
Note that this benefit is often over-sold. With more insulation in the attic or roof, the benefit of reflective roofing will be less — though it will still help in reducing the urban heat island effect (a general warming of urban areas, largely due to absorption of solar energy).

6. Consider thermal mass

In some climates, providing thermal mass in the house can help reduce air conditioning requirements. Use of thermal mass, such as a brick chimney, plaster walls, or slate floor, can help keep a house interior from getting too hot during the day.
Heat is absorbed by these high-mass materials during the daytime, and effective night flushing (see #8, below) can then get rid of that heat at night. This benefit is greatest in climates with large diurnal temperature swings.

7. Control moisture well

Humidity makes us uncomfortable and raises air conditioning requirements. House design for passive cooling should provide for absolutely no moisture seepage into basements, should have proper flashing to avoid rain entry (you’d be surprised at how often flashing is done incorrectly), and should have bathroom fans to exhaust moisture where much of it is generated. Bath fans should be quiet to increase the likelihood that they will actually be used.

8. Design the house to facilitate effective ventilation

When the outdoor temperature and humidity are low enough, homeowners should be able to ventilate the house, exchanging warmer indoor air with cooler outdoor air. It often makes sense to close up a house during the daytime and then carry out “night flushing.”
For this to be effective, enough operable windows must be provided. In hot regions where the night temperatures drop, such as the Southwest, an outlet vent high in the building, even a specialized cooling chimney, can make a great deal of sense. Whole-house fans can increase this night flushing significantly.

9. Install efficient lights and appliances

Lighting and appliances can introduce a lot of unwanted heat. A standard incandescent light bulb, for example, converts only about 10% of the electric current into light; the rest is emitted as heat. Fluorescent lights produce a lot less waste heat than incandescents, and the best LED lights today are even better.
More efficient appliances (refrigerators, dishwashers, clothes washers, etc.) also produce a lot less unwanted heat.

10. Provide ceiling fans

Ceiling fans keep us cool by increasing evaporation from our skin. With gently moving air from such a fan, we may be comfortable with air temperatures as much as five degrees Fahrenheit warmer than with still air. This may reduce the periods during which mechanical air conditioning is needed.

7.10.2013

That's what I'm talking about

A Net-Zero Passivhaus Duplex in Portland

A two-unit project in Portland, Oregon, should generate as much electricity as the occupants use

Posted on Jul 5 2013 by Scott Gibson
In Portland, Oregon, both units of a two-unit Passivhaus project sold before they were complete — one of them after being on the market for only two days and the second before it was ever listed with a real estate agent.
The net-zero energy O2Haus is the work of PDX Living, a company that is co-owned by Rob Hawthorne and Bart Bergquist. An earlier duplex project in Portand, called TrekHaus, was described in a GBA post by Richard Defendorf early last year.
The 02Haus units are 1,690 sq. ft. each, with three bedrooms, two bathrooms, and a one-car garage. Hawthorne says the project is the first net-zero Passivhaus spec project he's aware of in Portland. The project is in the Montavilla neighborhood.
After the first unit sold, the company had hoped to complete the second unit and schedule an open house before listing it. "But," Hawthorne said, "a couple of people had heard about it and someone came in and said, 'Please, please take my offer.' It was hard to refuse it. So one of the units was never listed."
The units sold for $379,000 and $405,000. He called the quick sale of the properties, at or above the asking price, a "good sign for the green building industry."

7.08.2013

8 Important advantages of Intus tilt/turn window

BURGLAR SECURITY

The tilt/turn window, when assembled with available accessories, will provide locking around the entire window perimeter. The many security features and Entry Resistant Fittings make your window into a "strong point".
EASE OF CLEANING

The cleaning of the tilt/turn window is easy and convenient as it is performed from the comfort of the inside of the room. No ladder or precarious positions to reach. Just open the window completely in the turn position. This will rotate the sash toward you.
MAINTENANCE

Because of the design of this high performance window system, maintenance is kept to a minimum. Adjustments are provided to assure proper sealing pressure throughout the long life of the window.

OPERATION
The operation of tilt/turn is simple and effortless. By rotating the handle into any one of the three standard positions, the window sash will respond easily no matter how big or heavy the sash.
PERFORMANCE

Modern tilt/turn windows close tight. Cold, heat and noise insulation are unrivaled by any other window system. These unwanted elements remain where they belong - outside.

FIRE ESCAPE
With the window in the full open position you create a 100% unobstructed opening producing a fast and convenient exit in any emergency.

VENTILATION

In the tilt position, the window provides draft-free fresh air exchange while maintaining burglar security. The window cannot be operated from the outside of the room.

AIR CIRCULATION
A tilt/turn window can be opened completely in the turn position providing rapid air exchange when required.