Having an effective green envelope is the most important aspect of an energy efficient building. While insulating and caulking may keep your indoor air in, reduced airflow can result in a build-up of pollutants and a reduction in your indoor air quality. While concern for indoor air quality is well founded, reducing the efficacy of your building envelope is not the right solution.
The EPA lists poor indoor air quality as one of the top five health hazards. There are a number of culprits that contribute to poor air quality from the cleaning products you use to the air fresheners in your bathroom. These harmful chemicals combine with off-gassing from paints, furniture, carpets, and building materials which include formaldehyde and petroleum distillates.
Poor indoor air quality is responsible for a range of symptoms including nausea, fatigue, respiratory illnesses, headaches, irritation of the eyes, skin, nose and throat and allergy symptoms.
There are many reasons why a tight building envelope is essential to energy-efficient homes. A secure building envelope will mean that your energy bill will be reduced by 25-40%. A leaky building envelope can also allow moisture into the home which leads to damage and mold.
While your building envelope can never be tight enough, there are ways in which you can ensure that your indoor air is fresh and clean. The first step is to monitor the quality of your indoor air by installing a CO2 sensor. Ideally, this will be connected to your mechanical ventilation system which will open the damper when CO2 build-up reaches a certain level.
Some builders may recommend the installation of Energy Recovery Ventilators (ERVs) or Heat Recovery Ventilators (HRVs), but Richard Rue, building envelope expert from Energy Wise disagrees: “….have at least 10% glass to wall ratio… In nearly every case, if you meet the 10% glass-to-wall ratio, you will have enough natural leakage into the house that you don’t need to use any sort of air-to-air exchanger.”
A simpler solution is to fill your home with some floral friends. Plants are able to absorb 60% of carbon dioxide and VOCs and convert them to oxygen in a process known as metabolic breakdown.
Air filters offer another solution to poor indoor air quality. Air cleaners are usually designed to reduce particles in the air and are not effective in reducing gaseous pollutants. The effectiveness of your air cleaner will depend on a number of factors, from the EPA: “The effectiveness of an air cleaner depends on how well it collects pollutants from indoor air (expressed as a percentage efficiency rate) and how much air it draws through the cleaning or filtering element (expressed in cubic feet per minute). A very efficient collector with a low air-circulation rate will not be effective, nor will a cleaner with a high air-circulation rate but a less efficient collector. The long-term performance of any air cleaner depends on maintaining it according to the manufacturer’s directions.”
The answer to the question: “Is my home too airtight?” is a resounding no! Your building envelope can never be too tight and you must find other solutions to poor air quality. Whether you use indoor plants and living walls, air filters or mechanical systems, you must ensure that your indoor air is healthy.