A Breath of Fresh Air

With the Salt Lake Valley locked in one of its regular winter inversions, this would be a good time to mention another key green feature of the house we are building. Pictured above is the heart of the Heat Recovery Ventilator (HRV) system that was recently intalled. The purpose of this system is to provide an energy efficient way of bringing in fresh filtered air while removing stale air. HRVs are recommended by the American Lung Association. They are especially critical in this house, since the house envelope will be "tight," much like a zip lock bag. But the problem then becomes ventilation. The HRV is intended to meet that need by bringing in fresh air from the outside (notice the vents in the outside wall in the first picture), preheating the incoming air during the winter and precooling it during the summer. The HRV provides clean fresh air while keeping energy costs low. The picture above shows the HRV unit which houses the heat exchange core.

The HRV unit is connected to existing ductwork in the house, therby enabling it to collect stale moist air from the kitchen, laundry and bathrooms. This stale contaminated air passes through the HRV and is exhausted to the outside. A separate ducting system draws in fresh clean air from outdoors. As the two streams pass each other within the heat exchanger core, heat is transferred from the outgoing stale air to the fresh incoming air. The HRV unit is able to capture up to 85% of the energy from the outgoing stale air. Filtered, preconditioned air is then delivered thougout the house.

We are excited about the possibilites for better health resulting from cleaner fresher air. Allergies have long been a nuisance for both of us and this system should have a positive effect in reducing those symptoms. One of the culprits in many tight houses is the build up of carbon dioxide just from breathing. Other pollutants include household chemicals, carpeting and construction materials. Excess CO2 can cause headaches, general lethargy and grogginess. While our green builder (PCR) is doing everything possible to reduce harmful emissions, we believe the HRV will make us breathe even easier.

Light! More Light!

One of the green features shown in this latest photo is the use of windows to achieve natural lighting. The large windows pictured here are oriented to the southeast to capture as much sunlight as possible during the winter months. A sun shelf will be installed later to shade the windows during the summer months when the arc of the sun is higher. We will also plant deciduous trees on the southwest perimeter to provide shade during the summer. We have had good experience in our previous home with birch trees and will probably be looking at them for shade at this location.
Also pictured here is the clerestory (pronounced "clear-story"), which is another important source of natural light. Clerestory windows are a critical passive solar element. They are an architectural detail found in many churches and other buildings and are arranged in rows above the main building. Because they are higher than the surrounding roof and above eye level, they do not compromise privacy while providing an entire level of natural sunlight. In our case, the row of windows is located on the eastern side of the clerestory (not visible in the picture) and on the north and south sides. They will catch the morning sunlight very nicely, thereby reducing the need for electrical lighting.
The clerestory windows will also be operable to allow for natural ventilation. That process will be augmented by ceiling fans. Given their height, they will be operated by remote control. The window on the south end of the clerestory may have to be shaded during the summer to avoid excessive heat gain, at least until the shade tree(s) reach maturity.
The other natural lighting feature that will be installed soon are the solartubes. More on that later.