Just Green Homes » Eco-Glossary

Relative Humidity

Daniel Bossenbroek — Fri, 22 Jan 2010 05:40:06 +0000

If you have drafty windows you may be experiencing some of the effects of Relative Humidity. Warm moist air hits the cold surface of your window, it cools down and some of the moisture in the air condenses on the glass.

Relative Humidity is a term used to describe the amount of water vapor in air at a specific temperature compared to the maximum capacity of the air at that temperature.

The benefits of high (20 – 30%) relative humidity in the winter are that the air feels warmer and it doesn’t dry out your skin so fast. In the summer, high relative humidity known commonly as just “humidity” is what makes a 90 degree day turn to a swealtering day.

The goals are to increase the realative humidity in your house in the winter without causing it to condense on the windows, while in the summer keeping it as low as possible. This is one of the primary mechanisms that your air conditioner uses to make the air in your house feel cooler.

Solar Heating

Daniel Bossenbroek — Fri, 27 Nov 2009 06:05:36 +0000

R-value:

Daniel Bossenbroek — Sat, 07 Nov 2009 06:20:15 +0000

A measure of how well or poorly a material resists conductive heat flow through it. Insulation has a high relative R-value, while solid materials like concrete, glass and stone have low relative R-values. This value increases linearly with respect to the thickness. R-value only takes into consideration conduction and does not address the other two modes of heat transfer: convection and radiation.

Building Envelope:

Daniel Bossenbroek — Sat, 12 Sep 2009 05:45:32 +0000

This is the barrier between the inside and the outside of your house. It consists of generic elements such as exterior walls, windows, doors, roofs, ceilings and floors, and specific elements such as vapor barrier, weather stripping, insulation, glazing, and exterior finish materials. It’s purpose is to limit fire, heat and water vapor flow through it and to keep may exterior elements such as rain, groundwater, noise, vibrations, pollution, odors, insects, and vermin out. The building envelope is also used to control the flow of light and solar radiation into the house.

Thermal Mass:

Daniel Bossenbroek — Tue, 18 Aug 2009 02:53:30 +0000

A building material, typically one that is fairly dense such as stone, ceramic tile, concrete, plaster or brick that is used to store heat and reduce temperature fluctuation in a space. This is accomplished when the material absorbs heat while the air is warmer than it and then releases heat slowly over time once the air temperature has dropped. Thermal Mass is typically employed in conjunction with passive solar heat.

Solar Collector:

Daniel Bossenbroek — Sat, 08 Aug 2009 04:15:46 +0000

Any device used to capture or concentrate the sun’s energy which can then be used for another purpose. Solar collectors come in many forms they can be a south facing window, solar thermal panel, solar electric panels (photovoltaic), a coil of black hose, or dark surfaced thermal mass.