[GSBN] The mechanical ventilation debate

[John Straube]

Felie, I think you and Robert have probably helped understand the "divide".

For people who dont use fridges, or more broadly, measurable amounts of fossil fuels and even worse, electricity, the entire discussion about airtightness, and even insulation, is not relevant.  In these types of buildings, like tents, we have a whole different set of design concerns, and high levels of airtightness is not worth talking about.  
I was implicitly discussing the 99% of homes 1 billion people live in the western live in.  There are literally billions more people lined up trying to build and get into this type of housing, so the conversation, and the understanding of different types of housing is really important for the environment.

People have been building shelter for thousands of years- the reason they built it was to control the interior environment.  Control the people and animals who can enter/leave, control the temperature, light, sound, rain, view, fire, etc.  So, the issue in design and construction is what to control, and how to control it.  It seems that those who advocate leaving windows open in winter for fresh air, or wearing sweaters inside in winter (to avoid simple, low environmental impact options that avoid requiring this) are merely drawing the control line somewhere different than the mainstream.  Thats OK by me.  If you desire 15C in winter, go ahead.  The only problem is, a billion people use a lot of energy to keep the temperature in their houses somewhere between 17 and 22 (according to measurements in numerous countries).  Smaller scale studies show that if you provide homeowners with a low cost means of controlling the temperature (insulation airtightness and good equipment) they tend to run it closer to 20C and the low temperatures go away and people say they are more comfortable and happier.

So, if you have a wider temperature range to make you happy, by all means design your house to do so.  Don't sell it to someone else though, or unless it is well insulated and airtight, it will be an environmental burden when the other 99% move in (like the old house of my neighbours).

But while making those houses, please dont make unsubstantiated claims about the poor health and safety of houses that are able to control the comfort and air quality with very few operating or embodied resources.    Airtight homes with mechanical ventilation have better air quality on average than homes built 20, 30, 50 years ago.  Homes with good airtightness and insulation survive interruptions in power for much longer with fewer problems than "old" leaky and uninsulated houses. This is a major advantage for them.  Airtight homes are not hermetically sealed freezers that children will suffocate in.  A ludicrous claim with no substantiation possible.  Tens of thousands of houses with 1.5ACH at 50 Pa have been built and survived power outages of various lengths, all with flying colours, with better outcomes than old homes.

I certainly share the concerns with "highly engineered" and complex houses.  Certainly I dont believe in such houses, although there is a modest segment of the population who wants their houses to be like iPhones, shiny glitzy and obsolete in a few years.  But I dont.  I want simple, robust houses that are affordable, comfortable, healthy, durable and, very importantly, consume as few resources over their life as practical.  Simple, airtight, insulated houses are one of the best formulas for achieving my list of goals.  There are others, but that is the one I choose.  And that is what enamours me of systems like straw bale.  They tend to be simple, square homes, with exceptional levels of insulation and the possibility (as Chris Magwood has proven) of being very airtight.

So I submit we may be talking past each other.  
I am trying to design houses for the 99%.
Others are trying to design for special needs (I guess lack of needs).
And yet others are looking for a social change that would make people not want electric lights, fridges, temperature ranges in the 20C/68F range.

If we dont confuse our goals, we may understand each other better.  Did I get it right?

On 2013-03-22, at 6:48 AM, Feile Butler <feile at mudandwood.com>
 wrote:

> I've been thinking about why has the mechanical ventilation debate been getting under everyone's skin so much. I think Robert Riversong's post echoes how I feel about it.
>  
> "what we now think of as a house has evolved from simple shelter to a highly-engineered machine that requires "operation" by its occupants in order to maintain a comfortable and healthy indoor environment."
>  
> John Straube made the point that we are all happy to use electricity for our fridges and computers, so why not our mechanical ventilation systems?
> 

Prof. John F Straube, P.Eng.
www.BuildingScience.com