Intelligent Ventilation Systems
The Texas Allergy, Indoor Environment and Energy (TxAIRE) Institute
An important dimension of high-performance buildings is their superior insulation envelope design. Today’s new construction is extremely "tight" meaning that little or no air leaks in through doors, windows, walls, etc. While this is extremely valuable from an energy efficiency perspective, it also means that increasingly we are living in a "thermos bottle". Therefore hand-in-hand with more energy efficient buildings is the need for mechanical ventilation and re-circulated air cleaning to reduce the build-up of potentially harmful gases, particles and biological (allergens, mold, bacteria, viruses, etc,) indoors.
Unfortunately in most existing homes, as the mechanical ventilation rate in a home is increased, the amount of energy needed to properly condition that air typically goes up as outdoor air in the summer needs to be cooled and dehumidified and winter air needs to be heated and humidified. (Otherwise we could just leave the windows open all year-round!) Additionally, and perhaps more subtly, outdoor air is not always “fresh air”. In many geographic locations, as a function of time of year, day of the week, or even time of day, outdoor air quality can frequently be worse than indoor air quality.
Thus high performance "green" buildings that are both extremely "energy efficient” and "healthy" should be smart enough to know "when to breathe in and out” and when to "hold their breath”. This simple concept underlies the reasoning behind our research and technology development agenda associated with "intelligent ventilation” systems. That agenda seeks to improve the energy efficient of building heating, cooling and ventilation functions through the use of "economizers”, energy recovery ventilators, and improved sensing and control. Taken together, intelligent ventilation implies the ability to sense both the indoor and outdoor environments and to make autonomous building control decisions that simultaneously optimize energy efficiency and indoor environmental quality.
Intelligent Ventilation in the TxAIRE Homes®
Several prototype intelligent ventilations devices made by local companies in Texas will be installed and tested in the two TxAIRE Homes®. A new residential "economizer" similar in principle to ventilation economizers regularly installed in the HVAC systems of commercial buildings will be installed and tested in one of the two TxAIRE Homes®. The device will sense and compare outdoor air temperatures and humidity with those indoors, using outdoor air to cool and heat the indoors when conditions are such that less energy will be used to bring in outdoor air than to cool or heat the indoor air using conventional furnace/air conditioning hardware.
The TxAIRE Homes® Initiative will also evaluate several different attic ventilation devices ranging from passive vents, wind-powered finned turbines, and solar powered fan power vents.