Friday, July 1, 2016

What is Passive House Comfort?

Superior Comfort is achieved Passively

Passive House is just as much about comfort as it is about energy efficiency. But what is COMFORT?

Passive Houses are ultra comfortable because:
1) They are ALWAYS Draft Free!
2) They are ALWAYS Quiet!
3) They are ALWAYS Let in Lots of Sun Light!
4) They are ALWAYS Warm!
5) They ALWAYS have Fresh Filtered Air!
6) Oh - they are ALWAYS Low Energy!

So lets talk "Comfort" for a minute... While writing this post I did an internet search for images of "Comfort" and after seeing photo's of Mattresses, Bra's and Lasagna and having a good laugh and some internal comments about our society I decided I had to narrow down my search to "Home Comfort".

There were 2 common themes:
Fireplaces, coffee, blankets and snow out the windows
Fireplaces are not exactly Passive House Comfort

So this is a little closer
White, bright, couches and smiles
Now - guess the season... You never know in a Passive House!

So, there is more to comfort than temperature

As mentioned above, the things that effect your comfort include:

  • Drafts - either near a heating or cooling duct, or near a window. In the insulation industry, drafts are the most common comfort complaint.
    • When the furnace kicks on you get a blast of cold air before it becomes hot. If your furnace is not sized properly you get this event more often than you should.
    • You typically feel this if you have inefficient glass (single or double pane) and warm heated air. The warm air will cool off when it hits the window and drop (since cold air is heavier than warm air). The dropping of air is the draft you feel. 
    • There are the most obvious drafts you feel that are coming directly from the outside. Through electrical outlets, under the baseboard, under doors, around windows, into the basement, etc. 
    • Drafts near chimneys are very common as well. Neither the glass doors nor the flu create a perfect seal. Cold air will drop and be drawn into the house.  

Not in a Passive House. There are no air leaks, there is no furnace, the windows are super insulated and there is no chimney. Drafts are an aspect of comfort that often get overlooked.
  • Noise - Have you ever heard a train blow it's horn, or your neighbor's dog bark at dawn on a Saturday or an airplane fly over, or those construction vehicles work near your house? We have all experienced this in a house before. But since we have just learned to live with it we don't realize how annoying these things can be. 
Thanks Floris from 475 HP Building Supply

Outside sound is not a problem in a Passive House (as you can hear from the short video from above). There is also no problems with noise from inside either. All of the mechanical equipment in the house is tested to operate almost silently. There is no Jet Engine noise from the bath fans (there are no bath fans), there is no swoosh of water from an upstairs toilet flush in the downstairs walls (from insulated drain pipes), there is no rumble followed by a winding noise from the furnace kicking on (there is no furnace). We have lived in noisy houses all out life and have learned to live with it without knowing we could do something about it. Passive Houses are quiet!
  • Daylighting
Another important aspect of Passive House is proper orientation. There is typically a lot of south facing glass. However when you utilize the Passive House windows they can be arranged on any side of the house. While we do utilize some of the passive solar techniques, they are not vital to the success of a passive house. In the Rochester Passive House - EVERY room has a window in it. In fact the 2 long walls of the house face East / West. We did what we could to maximize the southern window exposure and were smart about window size everywhere else. We even added a transom window in the 2nd floor laundry room to give that room some natural light.  
  • Surface temperatures (Not just heated floors)
The number one comment we get from clients looking for a high performance house is..."We have to have radiant floor heating". So comfort is obviously important and our clients have done the research and found that radiant heating systems are more comfortable than forced air systems.

The radiant floor heating typically will over heat a passive house. 

Passive House Design utilizes some Passive Solar techniques to help heat the house in the winter - with proper shading to ensure cooling in the summer. 

What exactly is radiant heat transfer? Well, without getting into Planck's Law, Stefan-Boltzmann Law and blackbody emissive power... It is essentially any materials ability to give off or receive infrared energy to other objects within a line of site of each other.


So in a typical room you are losing your Radiant Energy (body heat) to all of the cold surfaces around you (making you feel cold). Some of the more common surfaces are, the studs (or thermal bridges), the window surfaces, the cold tile floor, the cold granite countertop etc. All of them add up and pull your radiant energy to make you feel cool even when the air temperature is warm.

The idea behind radiant floor heating is warm feet plus a large warm surface in the house will offset all of the cold surfaces to make you comfortable.

Not Needed In a Passive House... ALL of the surfaces are within 6 degrees of each other - Window glass surface, basement slab, interior walls, tile floors, etc. So the radiant losses are never large enough to effect comfort - if anything they allow a lower air temperature to keep you comfortable.

  • Odors
How do you remove odors from your house now?

Open the windows
While this will give you the fresh air you need, it doesn't prevent pollen and dust from coming in as well. I'd also say this doesn't work too well in the Winter.

Turn on our Air Purifier
Cleaning the air is another common option. This doesn't however replenish the levels of Oxygen in the house.  Depending on the size of the purifier they also run off of 100 or more Watts. 

Maybe the most common...
Light a scented candle or use a scented aerosol spray to cover it up. 

If you don't think Odor Control is part of Comfort who are you kidding! Every Grocery Store I have even been in carries all of these products. If people could just live with the odors there would be no market for them.

There are problems with just covering up the odors - but I don't need to get into that. There are plenty of articles out there that will do that for me.
Article 1
Article 2
Article 3

There are plenty more, but back to fresh filtered air...

Passive House Utilizes a whole house ventilation system complete with heat recovery. This system runs off of 40-50 Watts (depending on if the ground loop pump is operating)

Fresh Air is drawn in from the outside, filtered and conditioned with the air to air heat exchanger. 

In the hottest and coldest months of the year the incoming fresh air is tempered by a glycol ground loop. In the winter it raises the temperature of the incoming air to near 40 degrees. In the summer it lowers the temperature to near 80 degrees (and dehumidifies the air). 

Now the tempered fresh air is filtered again before it enters an air to air cross counter flow heat exchanger. Here it reclaims about 86% of the heat from the stale stinky air from the house. 

The fresh, filtered, warm air is now distributed to the bedrooms and living spaces while the stale air is removed from the kitchen and bathrooms. Once the heat exchange takes place the stale air is blown outside

Every 3 Hours all of the air in the house is refreshed. 

Passive Houses are ultra comfortable because:
1) They are ALWAYS Draft Free
2) They are ALWAYS Quiet
3) They ALWAYS let in the maximum amount of Natural Light
4) They are ALWAYS Warm
5) They ALWAYS have Fresh Filtered Air
6) Oh - they are ALWAYS Low Energy!


  1. What did you end up doing for hot water and clothes dryer?

    Nice to see you in the Journal for Light Construction -{"issue_id":315890,"page":40}

  2. We have a whirlpool condensing dryer (Model WED99HEDW)[WED99HEDW]-1022543/WED99HEDW/.

    We will be installing a Sanden CO2 Heat pump water heater. The heat pump unit is located outside so there is no "air conditioning in the winter". A standard Heat Pump water heater will double our heating load.