In Permaculture

While the last post looked at conceptual flaws in the stages of design and planning, this list highlights bad home design decisions that can adversely impact home comfort and human health:

Bad Home Design Decisions: Toxic Building Materials 

1.) Sawdust Wood for Sheathing (OSB, MDF)

Oriented Strand Board

Oriented Strand Board.

Most modern-day homes are built with Oriented Strand Board (OSB) and Medium Density Fiberboard (MDF). These are technical ways of saying houses are built out of sawdust and glue. While I applaud the attempt to reuse materials and minimize waste, these products are loaded with toxic binding and anti-mold chemicals (formaldehyde, for one), and fall apart with moisture.

I think the fact that we are resorting to these materials is a sign that we are going in the wrong direction. We need to adopt a more holistic view of shelter and think about growing next generation’s building materials when we build our home. I’m personally looking to natural building, which aims to balance environmental impact, performance, indoor health, aesthetics, and long-term social costs. Buildings can be built from wood, straw, clay, hemp, and a plethora of other materials.

 2.) Vinyl Siding

Speaking of nasty chemicals, vinyl siding is one of the most horrible building materials on the market, period. It is toxic, has a short life span, looks terrible and emits volatile organic compounds (VOC’s). Its manufacturing process is also horrible for the planet. As if that weren’t enough, when vinyl siding catches on fire, it can burn so hot that it can ignite adjacent houses.

Don’t believe me? Do your own research. Go talk to your neighbourhood fire marshal. Check with local builders. Do an internet search. We are already surrounded by fire retardants in our beds, blinds and couches. Our paints offgas VOC’s. Our water systems exude chlorine, one of the worst offenders when it comes to indoor air quality, every time we flush the toilet or take a shower. No more. I’m leaning towards going all-natural when selecting a good covering material. My home will likely be straw bale, clay wood chip or light earth clay with a clay-based render and plaster. With the right eaves and maintenance, it will have a lifespan measured in centuries instead of years. It will also be non-flammable, produce no offgases and works with water instead of against it.

Bad Home Design Decisions: Windows

3.) Poor Window Selection 

In our cold northern climates, windows are the weakest links. A typical wall has a R-value between 8-20 (still too low, in my opinion), while an average window as an R-value of 2-3. Of course, poorly insulated windows are much cheaper. One of our biggest issues in North American is our attitude toward homes.  In many parts of Europe, homes are built not only for the next generation, but several down the road. We need to change our mindset towards seeing homes as disposable and temporary things. If you are choosing windows, do yourself a favour. Pick something that will keep you warm and will last a long time.

4.) Over-glazing

But just as easy as it is to underglaze it is also easy to overglaze the windows on a building. Overglazing can lead to an uncomfortable home that overheats in the summer and becomes difficult to warm in the winter.  Many people are surprised to discover that passive solar guidelines only recommend between 12-20% of their southern sun-exposed wall be covered in glass. Anything more than 12% and additional thermal mass needs to be added. More than 20% and the building will overheat and cause stress on its inhabitants. Also, take care when putting in large glazed northern windows. Northern light is wonderful to work with, but those windows typically lose more energy than they gain.

There are many excellent books written on passive solar design. If you are planning to build a home, do some research and learn to build it to run on the sun and to make it last centuries. Society sorely needs this level of leadership.

5.) Lack of operable windows and ventilation

operable window

Windows that can open bring in fresh air.

While windows light the house, operable windows allow the home to breath. Many people reduce the number of operable windows due to cost, but I think that’s a mistake. One of my favourite homes to visit is in the East Kootenays in British Columbia. A covered deck wraps around the house and keeps the solar gain down. The entire lower story is glazed with many operable windows. When the windows are open, fresh air flows in and makes you feel like you’re in an expansive space. When we forget windows, especially operable ones, homes can feel a bit like prison cells.

To optimize your home’s natural ventilation, you can check out programs that simulate airflow through a structure. They can help you quantify how many windows you need and where to place them.

Bad Home Design Decisions: Missing or Lacking Features

6.) Undersized Eaves

Eaves are essential for keeping a home cool and dry. Small eaves have become the norm, especially in cities where people attempt to maximize their indoor living space on 25-foot lots. I once spoke with a stucco installer who cursed these new homes because they constantly get called back to repair the water damage directly caused by undersized eaves.

If you want a house that’s going to be comfortable and durable, you need large eaves. There are many eaves design resources online that focus on the following objectives:

  • They keep the rain off the walls.
  • They eliminate summer solar gain.
  • They allow winter solar gain.

Correctly sized eaves fulfill all of these criteria. In addition, why not consider turning large eaves into a wraparound deck that you can use on warm summer evenings? Screen it in and you can sleep outdoors in total comfort!

7.) Lack of Vestibule/Air Lock

Modern homes have largely removed this intelligent energy-saving feature. Vestibules act as airlocks that keep extreme cold air out when people come and go. They add dead space that increases the insulation value of entrances while controlling infiltration. They also provide storage for items that don’t need to stay at room temperature. I’ve been people use them to get farm dogs out of the extreme cold without having to bring them completely inside.

8.) Lack of Mud Catcher in Vestibule

The best vestibules I’ve seen have mud grates that allow you to scrap your shoes and boots before putting them away. This feature keeps homes clean and provides a central location for annual cleaning. Simple and practical.

9.) Too Many Cantilevered Areas 

Home with cantelever

A cantilevered home.

Many newer homes have multiple cantilevers which reduce energy efficiency. These are typically seen on new infill homes, again, on 25 square-foot lots and are used to maximize square footage and add dimension to “boring rectangle” designs. But the home shape that works best in cold climates is a cubic or rectangular shape with the least amount of corners. The amount of gained footage through cantilevered sections is negligible while adding discomfort and heating costs. There are plenty of ways to add depth to buildings without resorting to cantilevers, including using different materials, adding windows, or using art. If you’re not convinced, go to one of your friend’s homes which lots of cantilevers. Stand in one when it is −30˚C outside. Trust me.

10.) Lack of Central Chimney for Cooling

In some ways our homes are difficult to design. Being in northern climates, we have extremely cold winters and extremely hot summers. Our solar insolation swings from extreme abundance to extreme deficiency. For this reason, it’s important to have a central stack, usually designed as a staircase in the centre of the home to allow warm air to rise. If the air has somewhere to go when it heats up, you can evacuate it out on hot days and provide a path for cooler air to enter through means like earth tubes (more on this next post). By using this natural buoyancy, you can bring about fresh circulation without incurring the energy costs of using a fan.

Next up: The Top Appropriate Technologies for Your Home.

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Showing 13 comments
  • rowan

    You stated above, “You want you thermal mass on the inside and insulation on the outside.”
    What if I have a large pole barn and want to add straw bales on the inside as insulation, and then section off areas to make rooms within the barn that can be heated individually? Will this work?

    • Rob Avis

      Rowan, this should work but I can’t say for sure. When we add insulation, especially insulation that can rot we need to understand how the vapour will move from areas of high moisture to areas of low moisture. It is important to understand this as we are always at risk of creating a dew point in the insulation as the vapour transits. If this happens in a straw bale it can rot.

  • Kari

    Hi Rob can you tell me more about the Central Chimney? I have a 1,082 sf bungalow 15% glass south side, metal roof adding on a wrap around porch. I live on a farm in SK on the open prairie and have chronic problems with roof turbines in 3 of the last places I have lived in MB and SK. The wind storms rip these off and they also leak water into the attic -house/quonset. On my house I removed a S.E turbine yrs ago with the intention of soffit vents – sounds safe out of the danger of the wind but does not follow the hot air rises principle so have been stuck in ponder mode for too many yrs on this one. Any suggestions on something that would be low profile that would stand the strong prairie winds and not look too inviting to the swallows and other birds always looking for some cheap real estate to build on? 😉

    Also in your last segment you talked about lack of insulation. What do you prefer for Attic insulation and exterior walls? My house was moved onto a new bsmt with R-Foil in my bsmt walls and bsmt floor (electric in-floor heat in bsmt and main floor), 1960’s buffalo board that came with the house, 3 deep pink insulation in attic that will need replacing due to poor ventilation in attic with only 2 gable vents. What do you prefer? Thanks!

    • Rob Avis

      A couple of years ago I installed a vented roof cap. It seemed quite durable but who knows in the wind you are dealing with. I think an actual chimney built out of wood, steel or brick would be best.

      Attic Insulation can come in many different forms. I use cellulouse as it is cheap and easy to replenish from time to time as it settles. We have 3ft in our attic. We had to put plywood down across the rafters to ensure the drywall did not come down.

      Basements are best insulated from the outside with foam or roxul. You want you thermal mass on the inside and insulation on the outside.

      Thanks for the comment.

      • Kari

        Thanks for the info Rob. A low profile roof cap sounds like a good idea! I had looked at Enviro Foam for my attic – not as green as cellulose but the brochure sounded ok – insulation made of soybean oil and recycled bottles, zero ozone depletion blow, lasts a life time and a plus for me -seals every nook and cranny to keep the farm flies out of the house (they would love cellulose!) … but it doesn’t seem to be as green as they would like you to believe? What are your thoughts?

  • Drew

    Good post Rob. Framing houses all summer, I’ve seen all too much of these poor features. Being from Calgary though, I think you missed one: Asphalt shingles that are so easily smashed to bits in hail storms! (and make collecting roof run-off questionable as well).

  • Janet Greenhalgh

    Rob, Thanks for the info. I am thinking of maybe using cordwood and mortar for ease of build. I have three questions:
    1)I thought passive solar homes had to be air tight. How can that be done with natural materials?
    2)If I am building a home into a south facing slope, are there any good natural materials for the foundation besides earth rammed tires or is concrete ok?
    3)Of all the books on passive solar houses, any in particular you recommend?

  • Ed Zaborski

    Rob, I’m a bit confused about your suggestions for % southern glazing (12-20%). If I recall correctly, Bill Mollison recommended a percentage approximately equal to the site’s latitude. I understand the concern about overheating in the summer, but wouldn’t adequately sized eaves that shade windows in the summer address that, while allowing greater solar gain in the winter when it is more needed?

    • Rob Avis

      It is overheating in the winter…ironically that you need to be concerned about.

  • Beth

    Love this article series. We are in the process of building a 1000 square foot south-facing, super-insulated, basement-less rectangle in Northwestern Ontario. There is so much conflicting information out there, it’s hard to know who is right. I’ve seen a lot of over-glazed homes (80s style passive solar) that are very uncomfortable to live in (overheating when it’s sunny, freezing when it’s not). Our new house will have exactly 20% glazing on the south side, and plenty of thermal mass in the exposed concrete floors. We are a little nervous that the floors will be cold, however, because they will not be heated (although they will be very well insulated underneath). The traditional wisdom about hydronic in-floor heat is being questioned quite a bit these days, with many people claiming it is not the right choice for small, tight homes–instead opting for ductless mini-split heat pumps, which is what our energy efficiency consultant has recommended for us (in addition to a centrally located wood stove). Anyway, I was just curious if you know of anyone else who has exposed, unheated (but insulated) concrete floors in our climate…whether they are uncomfortably cold and how useful the thermal mass is.

    • Rob Avis

      None come to mind but I will think about it. The homes that I have toured that are passive that have concrete floors were very comfortable. You can allways use a trough rug if need be.

      Thanks for the comment.

  • Chuck Draper

    4. Rather than reduce the percentage of south windows, we need to increase the thermal mass to absorb the heat gain. If the heat cannot get in through the windows, how can we expect to increase solar dependence.

    11. Under floor heating is a must. That is where the cold air is and that is where our most vulnerable extremity is. It is so important it should be in the building code.

    • Rob Avis

      Chuck, you are right to a degree. You can accomodate additional southern glazing with thermal mass up to about 20% of your south surface. Anything beyond that and you are going have dramatic over heating. Generally 12% – 20% is going to be the range depending on thermal mass options.


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