Over tight houses & under ventilated house

[John Raabe]

Lessons learned from the '70s - by Building Science guru, Joseph Lstiburek - always a fun and insightful read:

http://www.buildingscience.com/documents/insights/bsi-035-we-need-to-do-it-different-this-time



What you Don't want to see!

[MountainDon]

Great article. Just about anything Lstiburek writes is informative, easy to understand and entertaining.

[Homesick Gypsy]

Your subject line caught my eye because I have been wanting to write in and ask about a current "green" housing project I read about this week.  They claim R40 insulation on all walls, ceilings and floors and an envelope so tight that you don't need a furnace - in Maine no less.  Supposed to be heated by body heat of the occupants.  Nothing is ever said about ventilation.  Doesn't seem like that's healthy or safe.

[bayview]

Your subject line caught my eye because I have been wanting to write in and ask about a current "green" housing project I read about this week.  They claim R40 insulation on all walls, ceilings and floors and an envelope so tight that you don't need a furnace - in Maine no less.  Supposed to be heated by body heat of the occupants.  Nothing is ever said about ventilation.  Doesn't seem like that's healthy or safe.

   It would seem unsafe . . .    A good air exchanger would work well here.

http://www.airexchangers.info/air_exchanger_basics.html

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[John Raabe]

Yes, houses like that would need mechanical ventilation. In cold climates this would be heat recovery ventilation.

One of the real downsides of going too tight is that you want to be aware of this issue in power outages.

[speedfunk]

I will read this now .  As much as I wanted the house we are building to be 100% solar and efficient I was not going to sacrifice fresh air.


It seems like a lot of the air tight type construction I've found are just asking for a very sick environment for people.  if you have fresh air you can get away with a lot of VOC's.  But with air tight new construction you are going to sealing your self in this environment as everything off gasses not to mention breathing "dead" air.  Just a recipe for a host of illnesses. 

[John Raabe]

Many codes (such as the Washington State Energy Code) require mechanical ventilation in all new houses and have since the 1990's.

This can be as simple as setting up a central bathroom fan (a quiet one) on a 24 hr timer. This is the exhaust side of the ventilation system and the fresh air inlets would be in each bedroom and the main living space. These can be slot vents (with baffles) in the vinyl windows or through the wall vents in the bedroom closets.

Building a loose house at the framing stage is not the answer - doing this you can setup moisture transmissions and get condensation in unwanted places.



Click image above for the PDF booklet, or... http://www.arlingtonwa.gov/documents/Permit%20Center%20Applications%20&%20Forms/Bulding%20Permit%20Forms/53%20%20Ventilation%20Sys%20With%20Ventilation%20Exhaust%20Systems.pdf

[speedfunk]

John,

Running the a bathroom fan (on a schedule) is a really good idea.