“I don’t get it why would we want to make the house so tight that you would need ventilation?”

“I don’t get it why would we want to make the house so tight that you would need ventilation?”


I was asked this question by a potential customer. I think that this is certainly valid question. I answered it to the best of my ability within the short amount of time. I explained that the mantra of our industry is to seal it tight and ventilate it right. I explained the positive impact on IAQ and reducing the amount of infiltration from the dirty attic. I said our goal was make the house safe and comfortable and we would naturally become more efficient. That our repairs would work 24 hours a day hot or cold rain or shine.

I explained that the house was already tight and our measures would make it tighter and ventilation was necessary if the work was to be performed. ”but I keep windows open all the time” she replied. I explained that the ventilation would still be needed in case the windows were not open. And that filtered fresh air is a good thing. I explained that this is not a new thing as commercial buildings have been employing ventilation needs for decades. I also explained that current codes here in California have ventilation codes.

“Well I could see it if I had small children but I just don’t see the benefit.”  Our customer base is sometimes willing to listen and sometimes defiant. The fact is that these principals for a performance home are difficult for some folks to accept.  They do not understand nor see the benefit. Nor do they want change.

It is easy for most to grasp the concepts of insulation, duct sealing, windows (as misguided as much of the information is) high efficiency HVAC systems and Photovoltaic’s.  The highest hurdle for most of our customers to understand is Ventilation. The fact that we state we can save you energy and then require a device to be installed that was not currently in the home is counter intuitive. You can’t visibly see stale air or infiltration.

While good ventilation might have the highest positive impact it is in my opinion the hardest concept to sell.

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And again I agree: I did not bring Klingenberg in here, and I never created anything even near to gospel; we always kept passive house an open source - and again I agree, that's not the discussion here. The discussion was about air tightness and ventilation.

The scientific method has the power to be applicable everywhere. And, yes, results are different with different boundary conditions. Toxicity, embedded energy, ... that will be (almost) the same everywhere. And, increasing energy efficiency, done in an appropriate way, will help to reduce embedded energy, toxicity, ...

But, Robert, I do not need to discuss any of these if I'm not welcome.

So, let's agree to close this part of the discussion.


Your input is more than welcome. I am very pleased to have you reply to my thread with insights form Europe. We all have the same goal in this industry of creating a market for healthy and efficient homes. This forum provides a healthy area for interaction and exchange of ideas.  I will not apologize for the other gentleman's behavior as it is not my place. I will however offer my thanks for taking the time out of your day and responding to the discussion.


Your experience and knowledge was overshadowed by your impoliteness. I would suggest you take pause before you hit send. I think you have allot to offer but I for one will not listen if you do not work on your delivery and attempt to be more congenial.

That's your choice. I have little patience with anyone who insists there is only one standard for energy efficiency.

If you've been paying attention, the entire Passive House US organization was "decertified" by Wolfgang Feist and his PHI for daring to adapt his one-size-fits-all standard to the diverse climate zones in North America.

Feist insists that we use his German standard everywhere in the world and that anything more than 0.06 ACH50 is a dangerously loose house. The best building scientists and energy consultants in America disagree with him. But he does not tolerate disagreement.

There is no place for that kind of dogmatism in this field and if you fault me for standing up to him, it's your loss.

Maybe I missed something but since when did Mr. Feist say it is my way or the highway, there is only one standard & it is mine?

Lets cut the crap - the PHIUS group adopted the PH standard & then they started locking horns like you have done today with Ted (which you are right about the modeling aspect) & now Mr. Feist. Whether you like it or not - the Passiv Haus standard is the International standard & the organizing body is in Germany. That is pretty simple and if someone doesn't like it they can adopt LEED, ENERGY STAR, Green Goobers (come on you know you laughed a little), or simply create their own.

As for ACH50 - that is his opinion & there is nothing wrong with it if you do it properly. I think he has been more than tolerant with those that disagree & he tries to explain his views, takes & the science - sometimes it is just best to shake ones head and show some decorum

I guess you did miss it. Read this explanation of the "divorce" from PHIUS: http://www.passivehouse.us/passiveHouse/PHIUSResponds08.18.11.pdf

And this new blog on where PHIUS is going now that it no longer has to bow to Feist's dictates:


And it doesn't seem to be PHIUS that "locked horns" with Feist, but rather than Feist got upset that the real innovation was happening in America and he was losing his preeminence.

Let's not forget that the super-insulation movement began in the US and Canada in the 70's. Feist took what we developed and refined it and quantified it for the German climate. It was exported back to America but met resistance because it often didn't make sense in our varied and more extreme climates. It was modified for the American market and PHI tried to cut PHIUS out. Fortunately, PHIUS is refusing to be bullied and is proceeding to innovate and adapt to make PH a more applicable standard.

P.S. It was me who "locked horns" with Ted, either. He was belittling anything which contradicted his gospel.

I know about the breakup (and it's not limited to just one take), and where PHIUS wants to head & super-insulation, etc... The point is Passiv Haus standard is the standard & if someone wants to modify it they do so through channels or create their own - just because we are the US doesn't mean we always get our way

My .02 - I also agree with you on Ted & locking horns for the most part but you definitely come off as hard headed and the catch is not crossing the line from friendly discussions to completely adversarial (& no I am not saying Ted, me or anyone is perfect but this isn't the GBA and there are slightly diffrent rules) and I know you have a lot to offer this board & people on it



Nice to know there's at least one level-headed person here who doesn't resort to knee-jerk reactions.

Sixty years on the earth and 30 years in the field gives me a right to a hard head.


I too want to thank you for joining these discussions. Guidance about how to do things right is great, but possibly more valuable is experience around how and why NOT to do things can be priceless. In most areas of energy efficiency, Europe is years and sometimes decades ahead of us. This means you've made a lot of mistakes along the way. By sharing you might be able to help us avoid some big ones (to the extent we don't pigheadedly insist on making them).

And regarding Robert, maybe he had a bad week.

Best Reason for Mechanical Ventilation is Comfort.  When the occupants are uncomfortable, they do energy intensive things to obtain comfort.  And comfortable people are Happy People!

This morning the low temperature here was 71 degrees, it was 87 at Noon.  When I returned at 4 the temp was 96 degrees and the house was at 70 at 7:00 am and at 77 at 4:00 pm. The 'stat was set at 80 all day. I set the 'stat down to 75 at that time.

The mechanical ventilation allows us to feel comfortable at 75 from arrival home until bedtime.  Prior to air sealing and insulating last February, It needed to be 71 or lower for comfort.

I have two other clients that spent the money on my recommendation for continuous MV. They report similar comfort improvements with changes in 'stat settings that allow energy savings.

The feasible limit for tightening a home can be calculated two ways.

A) Cost Basis: The amount depends on Energy Price.  (All electric for ease of comparison). Columbia River Valley has relatively low rates around 5-7 cents.  Maine has 17 cents.  You can afford to do more in Maine then Oregon/Washington.

B) IAQ: You do what is needed to make occupants comfortable. 

- -

The comparisons of tightness are nice for Energy Folk like us to discuss.  They don't mean crud to people that live in homes, like my wife.  If she is uncomfortable, she will change the 'stat.  Doesn't matter if it is February, opening a window might trigger an allergy, now she also mentions having to dust after opening the window to let fresh air in. Most of my clients are like my wife. They have their reasons for not opening windows, allergy, safety, etc. 

I give them blower door results and recommendations in terms of Air Changes per Hour.  (ACH at 50). They almost always look at the manometer when doing the blower door test, so they see the CFM at 50 reading.  Many of my clients are engineers (aerospace types). 

Usually the decision to tighten the home and add MV is made by the wife. These guys understand air tight, they build airplanes airtight!  They question why houses can't be made air tight. I give them Dr. Joe's answer.

Let's not confuse IAQ with comfort - they're really two different things. A home can have poor indoor air without any feeling of discomfort until the occupants start developing allergies or chronic headaches.

Human comfort factors include:

  1. Clothing level
  2. Metabolic activity
  3. Air temperature
  4. Mean radiant temperature
  5. Radiant asymmetry
  6. Air convection velocity
  7. Air convection turbulence
  8. Air temperature stratification
  9. Relative humidity
  10. Color
  11. Noise
  12. Odor
  13. Glare
  14. Vibration

Pretty limited definition of comfort if you can have a headache or sneeze your head off!

Using your definition, comfort would come before IAQ.  So that makes it a good starting place. I am OK with that.  I want my clients to have both.  Those that have included mechanical ventilation are getting both.


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