Green buildings incorporate all sorts of environmentally friendly products, including those that conserve natural resources, save energy and water, or are made from recycled materials. Products that contribute to a safe, healthy building environment are also important in green buildings, and ventilation definitely falls into this category.
While proper ventilation should be a natural part of any home or facility - we all have to breathe, right? - there is a special emphasis on indoor environmental quality (IEQ) in green buildings. In most green structures, IEQ strategies must address moisture control, local exhaust, supply air filtering, radon protection, contaminant control, and yes, ventilation.
There are myriad ways to incorporate proper ventilation in any home, and builders of green houses often make use of natural ventilation, energy recovery ventilation, whole-house fans, energy-saving exhaust fans, or a combination of all these methods to achieve the correct amount of ventilation. Regardless of the type of ventilation used, green builders usually take a holistic approach to the structure in order to make sure that all systems and components work together in harmony.
GREEN BUILDING IS GOOD BUILDING
Green building is a catchy marketing term for good building, said Paul Raymer, chief investigator, Heyoka Solutions, LLC, Falmouth, Mass.“There’s really no difference between the ventilation system in a good building or a green building. If you’re interested in green building, though, you have to look at it from a holistic point of view. The holistic building considers all the issues involved, including handling of materials, waste, longevity of materials, comfort, safety, and a low-carbon footprint.”
Heyoka Solutions focuses on advancing the science, technology, and knowledge of holistic building through a multidisciplinary approach. The company specializes in creating fans with motorized closure systems for crawl space exhaust, bathroom exhaust, residential garage exhaust, and whole-house cooling, as well as pressure controls.
It also develops proprietary ventilation products for various companies, and company personnel teach classes on ventilation at various schools and conferences.
“Right now we’re working with some very advanced modular home builders, and they’re looking at a holistic approach to building homes, applying green technologies,” said Raymer.
“They might have specialists in insulation or moisture control, and we help them pull those pieces together and make them see how it all works as a system. Anyone can build a house, but pulling all the pieces together is important.”
Raymer noted that it’s not always necessary to have a mechanical ventilation system in a green building, but it is not practical to rely on occupant intervention for passive ventilation. He believes that there are plenty of ways to design a building in order to enhance air circulation. The problem is how involved the home- owners will be in utilizing the ventilation techniques provided, both passive and mechanical.
“If you’re in a climate that can handle having the windows open and people who live in the house will do it, then that’s OK. There are other ways of moving the air around without the mechanical systems, too. For example, some of the old building techniques have been lost, like the cupolas that were used to enhance stack effect and transoms that helped circulation in the building,” he said.
Builders of green houses often make use of natural ventilation, energy recovery ventilation, whole-house fans (shown above), and/or energy-saving exhaust fans to achieve the correct amount of ventilation. With a whole-house fan (shown below), exhaust can be ducted directly out. Leaving one intake port open in the attic will also exhaust hot attic air.
MECHANICAL SYSTEMS OFTEN NEEDED
Today’s tightly constructed homes usually need mechanical ventilation because adequate airflow does not come in passively. While just about any home can be retrofitted with a whole-house fan or an energy recovery ventilator (ERV) for better ventilation, in a green building, the mechanical ventilation system is part of an entire holistic approach to IEQ and energy efficiency.A good place to start looking for information on the holistic approach to IEQ is Energy Star’s “Indoor Air Package,” which addresses the entire list of IEQ issues, including HVAC systems, ductwork, moisture control, pest barriers, and radon control.
Under the ventilation section, Energy Star recommends that mechanical whole-house ventilation should meet ASHRAE 62.2 requirements and that the following requirements should be visually verified:
• Whole-house mechanical ventilation system and controls in-stalled to deliver prescribed outdoor air ventilation rate (62.2 section 4), including ventilation restriction in 62.2 section 4.5 (i.e., max 7.5 cfm/100 sq.ft.) for “Warm-Humid” climates as defined by IECC Figure 301.1;
• Transfer air (i.e., air from adjacent dwelling units or other spaces such as garages, crawl spaces, or attics) shall not be used to meet ventilation requirements (62.2 section 6.1);
• Air inlets shall be located a minimum of 10 feet from contaminant sources (62.2 section 6.8), and
• Airflow tested to meet rated fan airflow (at 0.25 inch w.c.), or duct(s) sized per requirements of 62.2 Table 7.1 and/or manufacturer’s design criteria (62.2 section 7.3).
In order to make sure the mechanical ventilation system performs per the Energy Star recommendations, Raymer believes that more product testing and verification is required.
“We need to make sure that the systems actually work. One of the problems is that someone might specify the rate that mechanical ventilation needs to achieve, but unless you measure it on an installed basis, you can’t be sure that’s really happening. Down the road, I see a requirement for performance-based codes.”
The Home Ventilating Institute (HVI) currently performs product testing, which is extremely useful in providing a level playing field, so consumers can compare apples to apples. However, Raymer noted that laboratory conditions can differ greatly from actual performance. “It’s unlikely that the contractor is going to measure the resistance of the ductwork to make sure the homeowner is achieving 60 cfm, which is what it might say on the box. Real-world conditions are considerably different from laboratory conditions.”
Regardless of the type of ventilation system that is installed in a regular home or a green home, the ideal system is carefully planned and designed, taking into account airflows, combustion air, range hood air, and the dryer, to name just a few factors. In addition, the airflow must be balanced, so everyone in the house is comfortable and the pollutants are removed. Green building practices are simply good building practices, and designing a proper ventilation system should be an intrinsic part of the process.
Publication date:10/22/2007
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