Indoor air quality is an important topic all year long – not just during winter when we’re spending more time indoors. Today we continue our series on simple things you can do to improve your indoor air quality, which we started back in March.

Read part 1 of this post.

In part 1, we told you that indoor air quality should be approached with four principles in mind: Elimination, reduction, ventilation and filtration. Part 1 focused on elimination and reduction. Today we are going to address ventilation, and more specifically, spot ventilation.

Spot ventilation, or point-source ventilation, exhausts air at the origin of the pollution.  This typically means using a simple fan to exhaust water vapor and cooking byproducts, which include smoke and combustion gases from a gas cook-top or range.  Water vapor also comes from bathrooms, pets, our own respiration and perspiration, and plants.  And yes – water is considered an indoor pollutant, especially when vapor accumulates. It can condense and collect on drywall, wood and other materials that are susceptible to moisture damage.  And if these materials remain damp, it creates the conditions for mold to thrive.  The good news is that controlling moisture in kitchens and bathrooms is easy and inexpensive to do.

Bathrooms

Bathrooms are among the greatest indoor sources of water vapor. One very inexpensive way to help control bathroom moisture is to use a bath squeegee. When you’re done bathing, squeegee off all shower or tub surfaces, including the tub or shower pan area. This substantially eliminates the water that would otherwise evaporate into the room. Eliminating water at the source is always easier and more efficient than removing it with ventilation.

Keeping your bathroom dry using ventilation is also fairly simple and inexpensive.  Although newly constructed homes automatically have bathroom fans installed, older homes may not, or, the fan may not work properly, or is very loud making you not want to use it.  Follow these three key aspects to make sure your bathroom ventilation is effective:

1) Install a quality fan

Energy Star bathroom fans are a slam dunk in terms of efficiency and quiet operation.  To qualify for the Energy Star label, the fans must be quiet (2-3 sones or less), and electrically efficient.  For quietest operation, look for a fan with a very low sone rating – this is a measure of the fan noise projected into the room – a rating of 1. 5 sones or less is excellent.  Matching existing bathroom décor is easy, as a wide variety of colors, styles and sizes of fans are available.  Picking the right “sized” fan, or how many cubic feet per minute (CFM) you need is also easy.  California Building Code requires a minimum of 50cfm for a fan that is run intermittently and 25cfm for a fan that is run continuously (some fans can run at a very low level around the clock).  For larger bathrooms with jetted tubs or multiple fixtures, see Home Ventilation Institute’s “Home Ventilation & Indoor Air Quality Guide.”

2) Make sure your fan is installed, supported and vented properly
Once you’ve selected a properly sized Energy Star fan, make sure it’s installed using best practices.  Fitting the fan snugly into the drywall is important to make sure that moisture laden air does not sneak between any gaps between the fan and the ceiling.  This edge can be filled in on the attic side or bathroom side with regular painter’s caulk.

Use sheet metal duct, sealed at all edges and joints with mastic (not tapes) and fasten with three metal screws in each joint, and avoid sharp angles or elbows near the fan.  Join this duct to an appropriate roof jack, wall vent or other durable hood which vents directly outdoors.  Again, be sure the duct vents all the way outside and not into the attic. While tempting, this could quickly convert your attic to a mold farm.  Somewhere in this duct run should be a backdraft damper – it could be near the fan or the exhaust hood – but it should not be at both.  Consider serviceability when choosing where to locate the damper.

Finish things off with a vinyl or mylar backed insulation around the duct and seal all the edges with a matching tape.  This makes the duct quieter and prevents condensation in cold weather.  Finally, adequately support the sealed, insulated sheet metal duct with strong wire or other highly durable strapping material to the rafters.  This reduces stress on the fittings, fan and exhaust hood and is more durable if other attic work is ever undertaken.

3) Install controls that ensure your fan will run

With the fan and duct installed, you can use a standard wall switch to control the fan or you can use a fan control device.  This could be as simple as the classic “crank” or “twist” timer that provides up to 60 minutes of run time.  Or you could opt for a motion sensing/timer switch that runs the fan for a prescribed amount of time, but can be manually overridden when users leave the bathroom.  These will automatically run the fan if a guest is unaware of how to use it, and they allow you to manually set the fan for 30 minutes for example, after completing your shower and leaving the bathroom.

GreenPoint Rated recommends running a bathroom fan a minimum of 15 minutes after bathing.  Humidity sensing switches and fans are also available, but the durability and reliability of the sensors are still in question. Current California Building Code requires newly constructed homes to use an Energy Star bathroom fan with a humidistat control.

Kitchens

Like bathrooms, kitchens are a source of indoor pollution that is easily controlled with spot ventilation.  And because smoke, particulate matter, water vapor and combustion byproducts from gas appliances may be a danger to your health and the durability of your home, proper ventilation in this room is particularly important.

1) Install a range hood

Most homes have some form of ventilation in the kitchen- either a range hood vented to the outdoors or a recirculating range hood which circulates air within the kitchen. The best practice is to have a range hood vented to the outside. This prevents cooking vapor and particulate matter from entering the rest of your home.  In some cases, recirculation range hoods can be modified to vent outdoors. Consult the hood manufacturer for specific instructions on how to best install a duct to vent to outdoors. If you are renovating your kitchen or otherwise installing an all new hood and fan for your range, you have the opportunity to address the issue more comprehensively.

2) Choose a correctly sized fan
A too small fan will not be able to properly exhaust when many burners are in use, while a too large fan risks depressurizing the whole house.  When your house is depressurized, air from unhealthy spaces like an attached garage, a crawlspace, or an attic may be drawn inside.  Depressurization can also introduce carbon monoxide – an odorless, tasteless gas that can make you sick – into your home by back drafting a water heater or furnace flue, or a fireplace or wood stove. To minimize the risk of depressurization do not use a downdraft exhaust system.

California Building Code requires a range hood to have a minimum of 100cfm for a range hood used on demand. For hoods against a wall, HVI recommends a ventilation rate per linear foot of range of 100 CFM with a minimum of 40 CFM.  For an island hood, install 150 CFM per linear foot of range with a minimum of 50 CFM. The Home Ventilation Institute offers further guidance on fan selection.

I asked Judy Roberson, one of California’s leading experts on mechanical ventilation in homes, about high volume, professional grade or commercial style range hoods in a residential application.  She cautions that “professional or commercial range hoods are intended to be used with an engineered system, and installing them in homes should be avoided.”  Instead, she recommends “selecting an Energy Star labeled hood, which ensures efficiency, and it is quiet enough so people are more likely to actually use them when cooking.”  For optimal performance, she recommends “ducting fans directly to outside with smooth metal ducting and installing a backdraft damper for reasons of fire safety.”  She advises “carefully following range and hood manufacturer instructions for proper positioning and installation, and if the home has a heat recovery ventilation system, kitchen range hoods should not be ducted into them.”

Finally, an oversized range fan uses more electricity and speeds up air exchange in the home.  This means that in the summer when running air conditioning, or in the winter while running your furnace, you will be exhausting much of your conditioned air outdoors, which you would then have to reheat or re-cool upon its entry.

Check back in a couple of weeks when I will conclude this series with the topic of filtration.

—
Kris Knutson is a former Home Performance Contractor and consultant, and current Program Associate with Build It Green.  He manages the Ask an Expert Hotline, which provides California residents customized responses to green building questions for building professionals and the general public.  Submit a question!

The exterior of the Curiels' straw bale home. The deep porch overhang adds further insulation from weather.

Q: What was the original inspiration to build a straw bale home?
A: We were first inspired by an article in the Mother Earth News Magazine back in 1983.  They featured a number of different sustainable homes including one that was made from straw bale, an adobe, an underground home, and a yurt.  The article listed the pros and cons of each and we were instantly drawn to the straw bale construction for a number of different reasons:

• the beauty of  straw bale construction
• the ability to shape the walls how you want them
• it’s a quickly renewable material and a second cash crop for farmers
• it’s a fire resistant material
• it’s an easy material to build with, which keeps construction costs low

Some of the other building types featured had similar attributes, but none had all the pros that the straw bale home could offer.  The ultimate decision was made when I walked into a straw bale home open to the public in Redding.  It was 95 degrees outside and 65 degrees inside, and when I asked if the owner had air conditioning, she said “oh no.”  She even noted that when they first moved into the home they thought the thermometer was broken, because the temperature had stayed the same degree mark through the entire winter.  “The only time it moved was when we turned on the oven to bake some cookies, and then the temperature went up a bit.”
The ability to keep the house at the same temperature without heating or cooling really appealed to us, and the decision was literally made that day to have a straw bale house.

Interior wall detail. Straw bale homes have deep walls that give the interior a warm, protected ambiance.

Q: So straw bale really is easy enough that it could save any homeowner on construction costs?
A: Absolutely.  We had a straw bale raising party with 100 friends and neighbors that put together the exterior straw bale walls over the course of a weekend.  Afterwards, I did all the finish work on the bales with a laborer for the next two weeks.

Q: So what is the estimate of the total cost of your 3,000 square foot home?
A: The land was $210,000.  Land Improvements including the driveway came in at $50,000.  Building permits and payments to the city cost roughly $30,000. Total house construction came to $410,000

Q: That’s pretty impressive! Other than the straw bale aspect, were there any other strategies to make the home more affordable?
A: We got a large report on the solar power system.  We used some salvaged materials (lights, doors, wood).  We only needed a third of the lumber for a house of this size because of the straw bales used on the exterior walls.  And I installed a huge open shelving pantry instead of using cabinets which also saved wood and money.

Q: Some people believe that the overall mass of a passively heated and cooled home like one made with straw bales tends to feel like living in a cave.  How did building with this specific material affect the interior of your home?
A: We have two dormer windows on the south facing wall.  They look like the second story of the home, but really they are light wells.  Because they bring in so much light, I do not have to turn on any lights during the day.
Light wells alter the feel of the house and really make it feel open.  We have a neighbor whose house is five times as big as ours, but does not feel as open.  It’s because of the ceilings and the inkling light in our big great room.  Half of the first floor is entirely open.

The thick straw bale walls keep the home warm in winter and cool in summer.

Q: Is there anything you would suggest to individual homeowners looking to build with straw bale?
A: Yes.  I would recommend trying to minimize the cuts they need to make. This can be done during the drawing process and will save homeowners additional time during construction. We had a few walls that required us to do to custom cuts on the straw bale through from top to bottom and they took forever.

Good indoor air quality (IAQ) is important regardless of the time of year.  The EPA estimates that  “on average, Americans spend about 90  percent or more of their time indoors” and that “indoor levels of pollutants may be two to  five times higher, and occasionally more than 100 times higher, than outdoor levels.”  Poor IAQ has been connected to attention deficit disorder and asthma in children. Although IAQ is a complex subject, these four simple, core principles can help guide your thinking: elimination, reduction, ventilation and filtration.

I will address the four core principles in a 3 part series. In this first part, I’ll talk about elimination and reduction.

Eliminate – Start with Common Sources
Elimination of pollutants is the keystone of quality indoor air.  This means removing substances from the home which are known to be detrimental.

Start with things that can be easily eliminated by changing your behavior.  Candles (petroleum or plant based), incense, indoor smoking, and kerosene or propane space heaters are common sources of indoor pollution.  They all introduce a variety of harmful substances into the air, including carbon monoxide and other combustion gasses, and particulate matter, which can lead to respiratory illness, skin irritation or even death.

(Candles and Incense as Potential Sources of Indoor Air Pollution: Market Analysis and Literature)

Instead of burning incense, eliminate sources of foul odor, like emptying a litter box or compost bucket regularly.  Ventilating the room with outdoor air is also highly effective, and is the subject of part two of this series.  If you still want to add fragrance, consider thinly slicing an orange on a plate, or if you burn incense, light it for only a few seconds and then extinguish completely.  Simmering spices has been a traditional remedy for covering odors, but this introduces excess moisture into your home and should be avoided.

Instead of burning candles, eliminate the pollution by not using them, or use a battery powered LED candle or a colored LED or CFL bulb.

Cabinets with low levels of formaldehyde.

Next, take a look at the materials in your home. Formaldehyde is one of the most common and harmful substances found in composite wood products commonly used in cabinets, shelving, etc.  In new construction, sources of formaldehyde can be eliminated through careful selection of framing materials, built-in cabinets and shelving.  For existing homes, replacement materials such as trim or cabinets and furniture should be selected based on low formaldehyde levels.  In both cases, look for hard wood products or composite products complying with California Air Resources Board (CARB) Airborne Toxic Control Measure (ATCM) Phase II requirements for lowest emissions.

Finally, avoid “room vented/venting” or “flue-less” heating appliances, as they vent combustion gasses into the room.  When adding a room heater, install a direct vent fireplace or wood stove with a Canadian Standards Association rating of at least 60 %.  This ensures efficient operation and that exhaust gasses will be immediately vented outdoors.  Electric space heaters are an attractive option, but can cause large increases in electric bills.  Also, generators should never be run indoors, in basements or in attached garages.  They should be run out of the home and away from operable doors or windows.
Once major sources like these have been eliminated, reduce the level of remaining pollutants.

Reduce pollutants – Complete a Radon Test and Make Retrofits
The U.S. Surgeon General, the EPA and Build It Green recommend that all homes, both new and existing, be tested for radon.  Radon is an invisible, odorless, naturally occurring radioactive gas that comes from decaying soil and rock in the earth’s crust and can get trapped inside homes.  It is the second leading cause of lung cancer in the United States of America behind tobacco smoking.  There is no safe level of radon in a home, but your risk for illness is highly variable, varying from house to house and person to person.

Measure radon levels in your home by completing a radon home test kit, available at hardware, home improvement and online stores.  The one-time test calls for opening a small packet, leaving it in your home for a number of days, and sending it to a test lab.  These test kits, including the lab results, cost approximately $25.  Constant monitoring with an alarm can be done with a digital device, which costs about $150.  Knowing the radon level in your home, and considering other risks will help you decide if you need to consider a retrofit of your home to reduce exposure.  Retrofitting for Radon safety typically includes adding a vapor barrier to a crawlspace, sealing cracks in basements and installing a vent pipe.

Learn more about radon safety and mitigation.

Conclusion
Navigating the complexities of IAQ can be challenging, but by educating yourself and hiring a home performance contractor you can do something about the health of your home.  Home performance contractors specialize in whole-house solutions to improve air quality and comfort, reduce energy bills, intrusion of soil and combustion gasses, and unwanted odors.  At the same time they can give you an overview of the safety, comfort, health, durability and energy efficiency of your home.

Home performance contractor performing a blower door test.

Energy Upgrade California helps you find home performance contractors qualified to assess your home and make upgrades and offers up to $4,000+ in rebates to help cover the cost.  See a list of participating home performance contractors in your area and incentives at www.energyupgradeca.org

In part two, I will discuss ventilation.

For more information on these and other best practices, visit the free Build It Green fact sheet library.

—
Kris Knutson is a former Home Performance Contractor and consultant, and current Program Associate with Build It Green.  He manages the Ask an Expert Hotline, which provides California residents customized responses to green building questions for building professionals and the general public.  Submit a question!

© Frank Paul Perez, Red Lily Studios

Villa Terra‘s beauty has just as much to do with what you cannot see, as it does with what you can. Within the 18-inch thick walls of the 3,200 square-foot house is enough dirt to moderate the sun’s heat throughout the year. That means the interior stays cool during the summer months and warm during the winter months. Although considered a brand new home at the time of its completion in 2005, its historical character is drawn from the many salvaged materials integrated both underfoot and overhead. Read on to get an insider’s perspective on Villa Terra from its homeowner and architect, Noel Cross of Noel Cross Architects.

© Frank Paul Perez, Red Lily Studios

Q: Tell us a little bit about your home.
A: I started on the house when I received the original building permit in 2001. I was undertaking a lot of the labor myself, so we continuously worked on it and didn’t move in until 2004. After we moved in, we kept working on it a little bit. In 2007 BuildItGreen asked us to be involved in their home tours.

I started out building it as green and as environmentally sustainable as I could. This ultimately became the fundamental reason to do a rammed earth or a P.I.S.E. house (Pneumatically Impacted Stabilized Earth). The method creates thick concrete walls with an earth aggregate. We used it because we were trying not to use lumber and wanted the benefits of a passive solar house.

On the other hand, it was not done for cost-effectiveness. In the end we ended-up spending about $350 a square-foot; but the house is probably worth more because I contributed a lot of the labor myself.

Throughout the design and construction, my motivations from the beginning to the end where to be as green as possible.

© Frank Paul Perez, Red Lily Studios

Q: Can you elaborate more on your motivations?
A: Sure. Every material that went into the house was measured-up against the four parts of a life-cycle assessment, including where you source the material and the transportation (how far it takes to get the material) to the site. We wanted the materials that went into our home to as sustainable as possible. We are also concerned about the health of the interior space of our home.

© Frank Paul Perez, Red Lily Studios

Q: What are some of the more notably green aspects of your home?
A: In addition to a ground source heat pump, a radiant floor heating system, and the big thick passive solar walls, we have solar panels on our roof and we also integrated a lot of reclaimed materials throughout.

I shopped for several years for plumbing fixtures, ceiling finishes, and the like. We also have thousands and thousands of board feet of reclaimed lumber. The home has a reclaimed bathtub and reclaimed sinks.

We got a lion share of the framing lumber (9,000 linear feet) from a shopping center that was torn down for the nearby redevelopment of Santana Row, just five miles away.

We are also really proud of the fact that this building is going to last 400-500 years, as opposed to the 80-100 years of a normal wood-framed home. We really built it to last.

© Frank Paul Perez, Red Lily Studios

Q: What are some of the favorite outcomes of the home?
A: My favorite outcome of the project is the look and feel of it. My wife and I also wanted it to be quiet. Thanks to the thick walls – it’s very quiet on the inside. We really like the fact that it just feels solid, and the fact that it looked 300 years-old when it was completed.

It is also great, especially in the summer. You can walk in at 5 in the afternoon on a 100 degree day and it stays cool inside. The walls help it stay cool during the summer and warm during the winter. We really enjoy the effects of the passive heating and the passive cooling systems we have implemented throughout.

© Frank Paul Perez, Red Lily Studios

Northern California residents, join BuildItGreen for one of these FREE homeowner workshops, and get started on your green dream home with tips from GreenPoint Rated today!

Feb 1 | 6:30 – 8pm | Burlingame | RSVP
Feb 2 | 5:30 – 7pm | Berkeley | RSVP
Feb 4 | 1 – 2:30pm | San Francisco | RSVP
Feb 11 | 10 – 11:30am | Walnut Creek | RSVP

Read on to find out more about the workshops.

Whatever your reasons for remodeling, it makes good sense to use a green approach.

The rewards of green remodeling are tangible. You’ll reduce your energy and water bills, save on materials and maintenance costs, improve the comfort of your home, and eliminate harmful toxins.

Whether you’re planning a major remodel, or just sprucing up a bathroom, every change you make to your home is an opportunity to help the environment and improve your family’s health.

This 1-hour workshop will take you from basic improvements you can do yourself to more extensive changes that you can make with a building professional’s help. You’ll learn how each room in your house can benefit from easy, cost-effective fixes and get answers to some of the most common questions about green remodels, including:

• Where do I start?
• Will it cost more?
• If it’s green, will it still look good?
• Will it really save me money in the long run?

Let our knowledgeable staff show you how to approach each of your design choices so you can achieve a beautiful, healthy home that conserves resources for future generations.

Integrated in the passive solar design of their extraordinary sustainable residence is highly rated recycled-content insulation (to maintain a steady interior temperature year-round), a hydronic radiant-floor heating system with a high-efficiency condensing boiler (to warm-up the interiors as needed during the colder months), and several Energy Star ceiling fans throughout (in place of a central air conditioning system). Now that she has lived in the house for five years, we took a moment to interview the homeowner, Jackie, to ask her if she still loves her home as much as the day she moved in.

Q: What was the major impetus behind wanting to build a new home in such a sustainable manner?
A: We (Jackie and her husband) talked about building a sustainable home 30 years ago, before “green” was a common term. Back then it was just considered the sensible thing to do, rather than the “green” thing to do. We wanted to use the sun to warm the house, and the prevailing breezes to cool it – it really was just common sense.

Q: How did going green affect the cost of building your home?
A: There were certain things that didn’t provide enough benefits to justify the extra cost. We talked to the builder and the architect and decided that while some things make a statement, given the scale of what we were doing and where we live, they weren’t worth the added cost. For example, heating the household water with solar power, having gray water recycling, and having geothermal heating were all considered but rejected because they didn’t carry enough benefit for a house of this size in Menlo Park. Being completely off the grid also didn’t make sense to us.

Q: What are some of your favorite outcomes?
A: It makes us feel good, and we have something to show friends and acquaintances. We’ve been able to provide an example to the neighborhood. Everyone knew what we were doing and we had signs up during the construction process to inform them. It’s been educational and we’ve had thousands of people come through the house via green organizations, schools, and colleges.

Some of the things that make the house green are an advantage to us everyday. For example, it never smelled bad, because it has less harmful chemicals off-gassing in the interiors. The concrete thermal walls and cellulose insulation also make for a very quiet home. Given where we live in the Peninsula, there’s a lot of traffic, and we don’t hear it very much at all so that’s a benefit we get everyday.

Another benefit is that the interior temperature varies very little. This is because the home is built using passive solar and radiant heat, and it’s very well insulated. We don’t have central heating or a fireplace and we don’t have to have air conditioning because the windows are designed to get breezes from every angle. Finally the materials are so beautiful. We love our bamboo floors and the finish of our natural clay walls.

Q: Have the more sustainable materials you selected shown more wear and tear than typical materials – for example your floors and countertops?
A: We don’t really have a point of reference, as this is the first house we’ve built, but we have not had any problems over the past five years. One thing I can say is that there is very little difference in the look and feel of the materials from the day we moved in. When the builder comes over, he always says that it’s holding up very nicely.

Q: You seem very happy with the home. Is there anything you would have done differently?
A: We’ve been asked this question so often. Really, other than some little things, we wouldn’t change anything. We have an outside shower built that we’ve only used twice. That’s not necessarily a regret; rather, it is an expense that we could have done without. But really nothing else. I’ve tried hard to think of things, because everyone asks us that question. That’s really the only response we can come-up with.

Our architect Polly (Osborne Architects) knows us well, so she was able to design something that completely meets our needs. She and Drew Maran (our contractor), have been very active about building green from the start, so they were a good choice for us.