The Summer of HEAT and HUMIDITY - Passive House Comfort Performance

The Summer of HEAT and HUMIDITY
Passive House Comfort Performance

CAUTION: THERE IS SOME VERY TECHNICAL DATA HERE.

If you understand things like Psychrometric Charts, Enthalpy, ASHRAE 55 (comfort criteria), and Indoor Air Quality Metrics, you may like this post.


It has been a while since I did a blog post that didn't have to do with an open house, so I am going to be a little rusty - and buckle in, it is a long one!

As everyone knows, this has been a very warm summer, and we have been dealing with some very humid conditions as well. I thought that this would be a good opportunity to see how Rochester Passive House performs to the standards for comfort. You can also be the judge if you'd be comfortable.

The purpose of this post is to show how effective the "minisplit per floor" method of cooling is in a Certified Passive House AND to show how we maintained superb Indoor Air Quality despite Poor Air Quality warnings from the local weather stations. Here is the set up:

1) 9000 BTU Ductless minisplit is located in the Master Bedroom on the south end of the house

2) uHoo IAQ Meter in kids bedroom on North Side of the house.

3) Netatmo Weather Station located on the front porch out of the direct sunlight

I put the uHoo IAQ meter in the kids bedroom for a few reasons

1) I have 2 girls - age 8 and 6 who share a room (2 occupants = higher potential CO2)

2) This room on the north east side of the house on the 2nd floor seemed to me be to be the most difficult to cool

3) I care about the IAQ for my kids, so I wanted to see if there was a problem in their room

4) They have a pretty routine bedtime and wake up time every day, so I figured my numbers would be consistent between the days. (8pm bedtime, 7am wake up - YES EVEN IN THE SUMMER)

Now, our method for cooling with the minisplits were:

1) We kept the master bedroom door open every day and all night

2) We closed the kids door every night - they did open it a few times to go to the bathroom etc, and left it open. 

3) We did do laundry at our normal rate, about 5 loads per week with a condensing dryer

4) Our Zehnder system was on "normal" except for times of boosting (showers and cooking)

5) The minisplit in the Master Bedroom was kept on "dehumidify" I figure it is trying to maintain 60% RH regardless of temperature. I can't find a good explanation on this anywhere.

6) Our 1st Floor minisplit was either set at 72F or Dehumidify - we change it around for comfort

Just How Hot Was it?

The typical HVAC design criteria for Rochester, New York is set for 1% and 99%. This means the outdoor temperature will only exceed the design temperature 1% of the hours of the year.  

Rochester NY Cooling Design Temperatures - from ACCA Manual J are:

1% Cooling - 86 F 50% RH

Because I will be discussing Temperature AND Humidity we will convert things to Enthalpy for comparisons. Simply put, the higher the Enthalpy, the higher the total heat content in the air. 

86 F with 50% RH has and Enthalpy of 35.3 BTU/lb

What does this look like on a Psycrometric Chart?

Okay, lets take a look at the outdoor weather from 9am June 28th - 7am July 6th

This is a mapping of temperature and humidity readings every hour for that 8 day period 

There are 191 measurements.

Of the 191 hours in this time period the Enthalpy for design was exceeded for 115 hours!

(There are 115 red dots above the red line)

I am not making an argument for or against the design limits set by ACCA, I am simply showing how hot it was over this week. 

60% of the time we were exceeding the design temperature limits for our cooling system.

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Lets Define Comfort

ASHRAE-55

"The purpose of this standard is to specify the combinations of indoor thermal environmental factors and personal factors that will produce thermal environmental conditions acceptable to a majority of the occupants within the space"

That is a lot to digest, so lets unpack that a little bit:
1) Thermal Environmental Factors - things like temperature, mean radiant temperature and humidity etc.
2) Personal Factors - things like the amount of clothing you are wearing, your activity levels etc.
3) A majority of the occupants - lets face it, we can't make EVERYONE happy, some people like it warm, others like it cool.

There are a few different models you can use to meet this standard -
1) Graphic Comfort Zone Model - to use this model you must meet the following criteria:

• metabolic rate must be between 1.0-1.3 - For intermittent activity, you take the average
• 0.7 - sleeping
• 1.0 - seated and quiet
• 1.2-1.4 - light activity
• 2.0 - walking, lifting heavy loads
• Anything higher has a low level of design accuracy
• Humidity ratio must be below 0.012 lb H2O/lb dry air
• that is 84 grains H2O per lb dry air

2) Analytical Comfort Zone Model - If either or both of your above criteria are too high, you use this method.

• Utilized this comfort tool model with inputs of:
• Operative Temperature (or Air Temperature and Mean Radiant Temperature)
• Air Speed
• Humidity
• Metabolic Rate
• Clothing Insulation
• These inputs are evaluated to predict a thermal sensation on a -3 (cold) to +3 (hot) scale
• You comply if the conditions show thermal "neutrality" between -0.5 and +0.5

Okay! WAKE UP! Moving On....

EN-15215 

This is the European Standard for comfort. 

For what I am trying to show within a Certified Passive House, EN-15251 and ASHRAE-55 are pretty similar. Since there is no temperature asymmetry and I am utilizing the residential standard for comfort (ie: we are not designing to maintain an exact temperature and humidity, like we would in a museum or hospital) the 2 standards are close enough without writing a book. 

I am simply trying to show how well we achieved summer comfort when the outdoor conditions exceeded our design conditions for an extended period of time.

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Comfort Criteria Assumptions:

• I will utilize the Analytical Comfort Zone Model via http://comfort.cbe.berkeley.edu/
• When the Kids are "sleeping" the MET will be 0.7 - 8pm-7am
• When the Kids are awake and during the day the MET will be 1.0
• The room is typically unoccupied during the day, but I have the data so lets look at it
• The Clothing Level (Clo) at night will be 2.0
• Kids in summer PJ's under a blanket on top of a mattress
• The Clothing Level (Clo) during the day will be 1.0
• The house is airtight, there is no ceiling fan and the way the ventilation system is designed there is no noticeable air velocity in the room. The Standard seems to have a 30 Feet Per Minute default, so we'll go with that (30 feet per minute = 0.34 miles per hour)
• The Mean Radiant Temperature is 77 F. This is a guess and tends to be the standard default. but there are no computers, electronics or other internal gains in the room other than the 2 girls. One alarm clock is the only thing plugged in. There is also 1 Passive House Window that faces east, so by 11 am it is completely shaded. The walls, floor and ceiling temperatures were measured with an IR Camera showing about 75.2 F

Kids Room Nighttime Comfort

So what does this mean?

• There were 96 hours where the kids were in their room "sleeping" over this time period
• The Average Predicted Mean Vote or PMV needs to be between 0.5 and -0.5. In this model the Average PMV is -0.06 - Thermal Comfort is achieved.
• The conditions in the bedroom stayed within the comfort zone (indicated by the light purple shading) the entire time.

Kids Room Daytime Comfort

• There were 95 hours during the day 
• The Average Predicted Mean Vote or PMV needs to be between 0.5 and -0.5. In this model the Average PMV is +0.07 - Thermal Comfort is achieved.
• The conditions in the bedroom stayed within the comfort zone (indicated by the light purple shading) the entire time.

You will notice a slight shift in the light purple comfort zone, due to different met rates and clothing levels. 

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So that is great, Thermal Comfort is achieved even when the temperatures are extreme for a long period of time. All without conditioned air distribution. But what about the indoor air quality?

The uHoo meter is measuring and data logging lots of air quality conditions every minute of every day. It also has tapped into the EPA's recommendations on limits for exposure on each. I get a notification when any one of these items exceeds the EPA's limits.

• Temperature -        Notification at 77 F
• Humidity -              Notification at 60 % (or below 35%)
• CO2 -                       Notification from 1000-5000 ppm - Warning over 5000 ppm
• Total VOC -            Notification from 400-800 ppb - Warning over 800 ppb
• PM2.5 -                   Notification from 50-100 ug/m3 - Warning over 100 ug/m3
• NO2 -                       Notification from 100-250 ppb - Warning over 250 ppb
• CO -                        Notification from 35-70 ppm - Warning over 70 ppb
• O3 -                          Notification from 55-70 ppb - Warning over 70 ppb
• Air Pressure -         Below 970 mbar or above 1030 mbar indicating a sever weather event

To save time and effort, I will omit the following readings since they didn't change the entire week:

Temperature and Humidity - I don't need to beat a dead horse

Carbon Monoxide = 0 ppm all the time

Air Pressure = 986.5-1003.6 mbar all the time

New York State Measures a variety of Outdoor Air Quality Metrics available to anyone at any time. Here is the Website link:
http://www.nyaqinow.net/

The Nearest Station to me is roughly 13 miles away.

Lets take a look at PM 2.5 measurements

PM2.5 is "Particulate Matter" that are 2.5 microns or less in width. That is a fancy way of saying "tiny dust". PM 2.5 is small enough that the body cannot filter them out when inhaled and thus enter our lungs and get absorbed into our blood.
According to the EPA you want to maintain between 0 - 50 ug/m3

My kids room vs. Ambient for the same time period:

The Blue Line is Outdoor Measurements from the NYS website.
The Orange Line is Indoor Measurements from the uHoo Device.

Over this time period:
the Outdoor Average PM 2.5 was: 10.8
 the Indoor Average PM 2.5 was: 6.1 (and never exceeded 8.1)

Lets take a look at NO2 Measurements

NO2 forms from ground level emissions related to burning fossil fuels from vehicles, power plants,
and off road equipment. According to the EPA scientific evidence links short-term NO2 exposure, ranging from 30 minutes to 24 hours, with adverse respiratory effects including airways inflammation in healthy people and increased respiratory symptoms in people with asthma. You want to stay under 100 ppb

The Blue Line is Outdoor Measurements from the NYS website.
The Orange Line is Indoor Measurements from the uHoo Device.

Over this time period:
the Outdoor Average NO2 was: 4.3
 the Indoor Average NO2 was: 0.5 (and never exceeded 0.6)

Lets take a look at Ozone (O3) Measurements

Ozone is not directly emitted into the air, but is created by chemical reactions between oxides of nitrogen (NOx) and Volatile Organic Compounds (VOC's) in the presence of sunlight. Breathing ozone can trigger a variety of health problems, particularly for children, the elderly and people with lung disease and asthma. You want to maintain levels as low as possible because breathing low levels over a long period of time may have more damaging and longer-lasting effects.
The safe level according to the EPA is under 55 ppb, however inhaling fairly low levels can still result in signs and symptoms such as coughing, congestion, etc.

The Blue Line is Outdoor Measurements from the NYS website.
The Orange Line is Indoor Measurements from the uHoo Device.

Over this time period:
the Outdoor Average O3 was: 38.6 ppb
 the Indoor Average O3 was: 4.0 (and never exceeded 4.4)

DISCLAIMER: Ambient Total VOC and CO2 are not currently measured by NYS.
I don't have data to the compare the indoor conditions to. I have moved the uHoo devide outside, and I taking some measurements to see how CO2 and TVOC (and all of the other measurements for that matter) varies. That data will be posted when I see something interesting.

Lets take a look at Total VOC Measurements

VOC's are carbon based chemicals that are emitted as gases from solids or liquids. While most people can smell high levels of some VOC's, others have no odor. There are thousands of different VOC's produced in our every day lives (Paint, Cleaning Solutions, Wood Products, Cooking, Air Fresheners,etc. etc.). The EPA recommends adding ventilation when above 400 ppb, and avoiding concentrations over 800 ppb.

The Orange Line is Indoor Measurements from the uHoo Device.

Over this time period:
 the Indoor Average TVOC was: 64.5
The 400 ppb limit was exceeded for 2 hours with a max reading of 471.9.

There is no direct correlation between an outdoor measured condition and the indoor condition for TVOC. I have been reading TVOC measurement outdoors as of late and have seen readings as high has 317 ppb, so it is plausible the indoor VOC spike was caused from an outdoor concentration spike.

Lets take a look at CO2 Measurements
CO2 concentrations are generally related to the number of occupants. It is usually highest where people and pets spend most of thier time. Some other sources include, combustion appliances, and from experience - bread baking (and rising). CO2 is generally considered to be 400 ppm in outdoor air. The ideal state is under 1000 ppm in the house. Elevated levels can lead to drowsiness, but no serious health effects until you exceed 5000 ppm. Headaches, increased pulse rate, decrease in cognitive thinking etc. can result.

Our ventilation system is designed to maintain roughly 600-700 ppm CO2 in the house (or 200 ppm above ambient).

The Orange Line is Indoor Measurements from the uHoo Device.

Over this time period:
 the Indoor Average CO2 was: 795

The 1000 ppm limit was exceeded on 5 occasions.  There are a few reasons for this.

• Outdoor ambient CO2 was likly high. On recent warm muggy nights I have seen the outdoor CO2 creep up to as high 632 ppm. 
• Ventilation Rates not high enough with high ambient CO2. While the system is designed to keep the CO2 levels in the 600-700 ppm range, it does consider that our winters are longer and CO2 concentrations are lower in the winter. 
• Extremely warm and humid nighttime temperatures are difficult for any cooling / ventilation system. 

We have an interesting dilemma here. On the worst night for CO2 concentration, our low temperature was 75.8 F with a 86% RH. If we increase our ventilation rate to lower the CO2 concentration we jeopardize the indoor comfort levels due to excess humidity. We do have an ERV, but when it is used in conjunction with the Comfofond typically it runs in bypass. This is because the Comfofond is lowering the temperature of the incoming air below the temperature of the extract air (ie: "Free" Cooling). When it cools the incoming air with the ground loop, the fresh air is near the saturation temperature (meaning it is very humid, but cooler). Usually in the 65-70 F range. 

For more information on my ventilation system see my previous blog post HERE

Because the CO2 levels are only elevated for a few weeks out of the year; 
AND they are no where near the dangerous levels 
AND all of the other indoor air quality metrics are within limits 

We are certainly satisfying any concerns of comfort with a spot source cooling unit.  

Glazing Surface Temperature

Glazing Surface Temperature

DISCLAIMER: This is for informational purposes only, I only own an IR Camera and I am NOT a certified thermographer. I know enough to be dangerous, and that is about it!

Here is my attempt at figuring out the glazing surface temperature at Rochester Passive House. I did 2 different scenario's.
                 1) Full Solar Gain - South facing window
                 2) No Solar Gain - Breezeway (north) door glass

Here were my test parameters:

                                         Full Solar Gain:                                 No Solar Gain:

                                 

The difficulty with finding an actual glazing surface temperature is glass tends to reflect quite a bit, so you are not reading the glass temperature, but the temperature of what is reflecting on the glass.

You can see my reflection in this IR Photo. 

To get closer to an actual glass surface temperature I took a scrap piece of paper, and covered half with black electrical tape, and covered the other half with 2 layers of painters tape. I taped this square to near the center of glass and let it sit there for a while. I am going to assume the paper will become the same temperature as the glass.

This is the paper I taped to the glass. I needed to make sure the paper was completely opaque. I used black electric tape for half, and 2 layers of painters tape for the other half. According to FLIR electrical tape has an emissivity of about 0.95. The painters tape is not as shiny (lower emissivity) but I wasn't sure if how the black tape would show a hotter temperature with the solar gain. 

Here is the Solar Gain Photo:

You can see, the black tape is hotter than the painters tape. But both of them are in the 103-106F range. The hottest temperature is not centered in on the black tape because of the angle the sun is hitting the exterior glass.

I have 2 images for the shaded glass

This one was taken roughly 1.5 ft away at a slight angle. It is roughly 65F

This one was taken about 6" away, but you can see how varied it is, there is quite a bit of reflection going on - but the average temperature is about 62 F

Because I was going in and out of the breezeway multiple times, the breezeway door and interior walls may be a few degrees cooler than normal. I took an IR photo of the interior wall, next to the breezeway door and it was 65F. I didn't post it because it is just an orange square - nothing really to see. 

Summary:

IN WINTER EXTERIOR CONDITIONS

Glazing Surface Temperature of South Windows in full sun = 100-105F

Glazing Surface Temperature of Windows in full shade = 60-65F - within 7F of indoor air temperature.

 Someday I am going to do this with an Energy Star Window and compare. 

Thermal Imaging Scans or Rochester Passive House

Rochester Passive House Thermal Image Scan

To close out 2017 I thought it would be a good idea to do on IR scan of the house while it was really cold outside to mimic my Summer IR Scan. Here they are:

Rochester Passive House Summer IR Scan

Rochester Passive House Winter IR Scan

 

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.

Huh??? 

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!