Posts Tagged ‘Relative Humidity’

What is my house doing to me?

November 22, 2016

Fall River, MA

hhe-kitchen-hazards“Why do I wake up in the morning with a headache?”  “Why is the house so dry in the winter?”  “What are VOCs?”  “Does my house have a radon problem?”  Can you answer all these questions?  When we do an energy audit on a home, we are looking for issues that impact the heating and cooling loads.  But the same tools that we use for thermal analysis can be used to highlight unhealthy or hazardous conditions in a house.  The BPI Healthy Home Evaluator (HHE) certification merges energy efficiency and home health together.

On Tuesday the 15th and Wednesday the 16th of November, a first in the nation BPI HHE class was held at Bristol Community College.  The BPI credential was developed in partnership with the Green & Healthy Homes Initiative.  “It builds upon the BPI Building Analyst (BA), Energy Auditor (EA), and/orbpi-logo-4c Quality Control Inspector (QCI) certifications to verify competencies required to conduct in-depth healthy home environmental risk assessments.  The Healthy Home Evaluator assesses home-based environmental health and safety hazards and provides a prioritized list of recommendations to address those hazards.”

The two day class extensively reviewed numerous aspects of HHE skills including the liability issues involved in stepping into a hazards and health analysis, resident interviews, the identification and interpretation of hazards, and the seven “Keep Its” developed to clarify the primary elements of the program:

Keep it:

  1. Dry
  2. Clean
  3. Safe
  4. Ventilated
  5. Pest-free
  6. Contaminant-free
  7. Maintained

The class was able to apply these techniques to the test cabin located in the BCC weatherization laboratory while going through a typical field analysis incgas-leaksluding gas leak detection, CO monitoring, combustion safety testing, blower door testing, and ventilation system verification.  Added to these was asbestos pipe insulation, messy counters including cigarettes and spilled coffee, long blind cords, children’s toys in the oven, toxic chemicals in a cabinet, and a hazardous carpet.  These hazards were so common and obvious that the students missed many of them despite the fact that they had been sensitized to seeking them out.  Like odor fatigue, elements such as these are so common in an energy audit that they are simply overlooked.

What are the Lower Explosive Limits for natural gas, propane, and gasoline?  What is the impact on house pressures of a blocked return air vent?  Is it a water stain on the ceiling or sign of a mouse nest in the attic?  There are dozens of questions about a house.  Some of them are no problem at all.  Some of them are chronic, long term problems, and some of the are acute problems (like CO) that should be addressed immediately.

This is an evaluation credential.  There is so much to know about this stuff that it will take years of testing and experience to know the ins and outs.  But if we can get homes safer and healthier it will save a great deal on medical care which should appeal to health insurance companies and all of us.

If you wanbristol-community-college-1t to learn more about this stuff, Bristol Community College will be conducting more of these classes at 1082 Davol Street, Fall River, MA 02720 – 774-357-3644

Healthy Home Evaluator Training

October 13, 2016

Fall River, MA     October 13, 2016

hhe-class2_troost-avenue For two days – November 15th and 16th – Paul Raymer of Heyoka Solutions will be teaching a pilot of the BPI HHE course at the Fall River campus of Bristol Community College (BCC).  The purpose of this course is to blend the knowledge of building science with the ability to recognize home environmental risks.

For years qualified building scientists have been striving to make homes more energy efficient.  The same tools can be used to recognize a healthy home environment.  Using their building science knowledge, students taking this course will connect what they already know to environmental concerns that are being overlooked.  The class, based on a course developed by Healthy Housing Solutions, is a combination of classroom sessions, group exercises, hands-on tool use, and situation analysis in BCC’s unique test cabin.  This class will review basic building science fundamentals and analysis tools that are used to apply the six Keep It principles: Keep It Dry, Keep It Ventilated, Keep It Clean, Keep It Pest Free, Keep It Safe, and Keep It Contaminant Free.

What is Integrated Pest Management?  What if the homeowner says the house is too dry?  What does that mean for energy use?  What does that mean for health impacts?  What impact do air fresheners have on the environment?  What impact do they have on energy efficiency?  What elements of a home environment might impact asthma in children?  What issues are chronic?  What issues are critical and an Immediate Danger to Life?

Consider healthy home evaluation an investigation, like CSI.  Understanding building science fundamentals can be lead to a clarification of a healthy environment.  A house is a system.  It’s all connected.hhe-class1_troost-avenue

Upon completion of the course students will be ready to challenge the BPI HHE 1.5 hour certification exam offered on November 17th.  Class will be held at  BCC – 1082 Davol Street – Fall River, MA  Phone: 774-357-3644

Contact Rosemary Senra at BCC for more information.

Homeowner’s Energy Workbook – Part 7 – The Skeleton

December 31, 2012

You need to get familiar with the skeleton of your house.  Most of our houses are framed with studs, commonly known as two by fours or two by sixes.  These are pieces of wood that have been milled from trees that are nominally 2 inches by 4 inches on a side.  (The milled pieces.  Not the trees!)  They used to actually be 2 inches by 4 inches, but with the fancy milling that goes on in saw mills, they are now one and a half inches by three and half inches or one and half inches by five and half inches.  This is important because there is now less space in the wall for insulation and other stuff.

Balloon Framining

Balloon Framing

Up until the late 1940’s the wall studs ran all the way from the foundation wall up to the attic framing.  This is known as balloon framing.  The studs had to be really long to go that far.  It’s handy for running wires in wall cavities, but it forms a chimney up the outside walls of the house.  The rising air (convection) can flow all the way up from the basement to the attic!  And with open floor cavities, it can even flow under the floors and up the inside walls.  This can make the inside of the house really uncomfortable.

Both because we had harvested most of the easily accessible, tall trees an because it is more convenient, since that time we have been using a platform framing technique.  Each level gets constructed individually.  The deck of the second floor serves as the platform on which to build the walls.  This technique makes the stud cavities in the outside walls shorter, limiting the convective loops.

If you start in the basement (assuming you have a basement), the Rim joist is at the top of the basement wall, connecting all of the first floor floor joists.  On top of that is the stud wall, reaching up to the Band joist that runs around the middle of the house, between the floors, connecting all the second floor floor joists together.  Then the second floor stud walls reach up to the ceiling rafters (unless you have a third floor).  The ceiling rafters form the ceiling plane, the top, inside surface of the house.  The roof is commonly framed with Trusses these days that are often built off site and trucked in.  In many cases the roof is framed with individual two by lumber on site.


Thermal Envelope

The Building Envelope is a term for all of the materials that separate the inside space from the outside space.  It includes the walls, windows, doors, floors, and roof.  Part of the building envelope is the Thermal Envelope or Thermal Barrier.  The space inside that is what is conditioned – heated and cooled.  It is the conductive heat barrier or blanket keeping the occupants comfortable.

Aligned with the Thermal Envelope is the Pressure Envelope or Pressure Barrier.  This is the convective heat/cool barrier.  The key to a comfortable living space is for the Thermal Barrier and the Pressure Barrier to be working together, to be aligned.  This is a really important issue that we will get into in more detail later.

I want to go back to that “house as a system” idea.  The floor, walls, ceilings, roof windows, doors are all part of the system. Except in “paradise climates” a house missing the windows would obviously not keep the occupants very comfortable.  If the walls were missing, that wouldn’t be much of a house either.  These are the extreme, and gratefully uncommon, conditions.

Let’s consider a house heated with fuel oil on a cold winter day.  If the oil runs out, the furnace can’t burn to produce heat.  The house cools.  If it gets cold enough, the water in the pipes starts to freeze.  As the ice in the pipes expands, it cracks the pipes.  When the outside temperature warms, the water melts and shoots out of the pipes, getting the walls wet.  The wet walls are a perfect breeding ground for mold growth.  And so on, and so on.

Again, this is a somewhat extreme system connection.  There are millions of much more subtle connections that are going on all the time in houses.  Many of them don’t mean much on a human time scale, but as houses get more efficient, the interactions, the systems become increasingly more interrelated, and the potential problems are amplified.  So we always want to ask before we start changing something, “What else is going to change if I do this?”

One of the things I have found living in an older house, is that one remodeling project seems to lead to a dozen more.  Changing a sink may require replacing the vanity, the pipes, the drain in the floor, the color of the bathroom walls, the floor covering, the towel racks, the lighting, and on and on.  The system unfolds before my eyes and a Saturday project becomes a Fall project!

Homeowner’s Energy Workbook – Part 6 (Definitions)

December 24, 2012

Stack effect on a Fireplace

Infiltration and ex-filtration relate to convective air movement.  Infiltration is uncontrolled air leaking in and ex-filtration, logically, is uncontrolled air leaking out.  How and where it leaks in has a lot to do with the pressures in the house.  (Remember, high pressure moves to low pressure.)  If the pressure is higher in the house than it is outside, air will move out of the house.  Warm air is lighter than cool air so it rises, increasing the pressure at the top of the house due to the Stack Effect when it is warmer in the house than it is outside.  The top floor ceiling of a house can have an enormous amount of pressure pushing on it, pushing air through any crack or hole or gap it can find.

A wise building science guy, John Tooley, once said, “Air is like crooked rivers, crooked people, teenagers and cheap labor.  It always seeks the path of least resistance!”  He also said, “Air doesn’t care where you want it to go.  It will always move through the closest and biggest hole.”

We have to have ways to measure things like pressure and temperature and airflow.  We measure temperature with a thermometer.  In the U.S. we measure it in degrees Fahrenheit named after Daniel Gabriel Fahrenheit in 1724.  Most of the rest of the world adopted the Celsius scale (after Anders Celsius) in the mid to late 20th Century.  The Fahrenheit scale has water freezing at 32 °F and boiling at 212 °F.  On the Celsius scale, water freezes at 0 °C and boils at 100 °C.  Seems a bit more logical somehow, but there we are.  We don’t deal with change well.

The pressure in buildings is commonly measured in Pascals, because houses have gotten so tight and the pressures are so small that using the inches of water gauge or iwg or inches of water column scale was too gross.  It would be like measuring a house in fractions of a mile!  Inches of water gauge is an indication of how far a certain amount of pressure can raise a column of water.  Iwg is the most common measurement for indicating pressures in heating and cooling systems and the operation of fans.  One iwg is equal to about 250 Pascals.  The important thing to remember here is to visualize how small a Pascal is.  It’s really, really small.  If we could measure a gnat’s burp, it would be about that small.  It’s a tiny amount of pressure, but it can make an enormous difference in how a building works and the health of the occupants.  We measure pressure using a manometer.  These days it’s common to use an electronic, digital manometer, but there are analog manometers as well.  The availability of digital manometers probably has done more for the advancement of building science than any other tool.  It has allowed us to measure very small pressure differences.  It has ushered us into the world of CSI for homes.

Testo 417

Large Van Anemometer

Airflow speed is measured in feet per minute (fpm), like miles per hour.  FPM is the velocity of the airflow.  The volume of air movement is measured in cubic feet per minute (cfm).  The volume of air moving through a duct or fan is indicative of a rate of heating or cooling.  Airflow is commonly measured with anemometers which come in a wide variety of styles.  There are large vane anemometers and mini-vane anemometers and hot wire anemometers.  There is a tool called a Balometer which is commonly used to measure airflows in commercial applications.  Airflow can be measured with a garbage bag or a bathroom tissue, but the numbers are not easily repeatable with these approaches.  Airflow can be measured using a manometer as well, by using the difference in pressure across a known sized hole.

You should also be aware of some of the nasty elements that can be found in homes.  Carbon monoxide (CO), for example, can kill people.  It results from incomplete combustion.  If the flue gases don’t flow up the chimney the way they are supposed to, they can “spill” down into the house and make the occupants sick, exhibiting symptoms similar to the flu.  More about CO later.

Radon is a gas that emanates from granite in the ground.  Radon can leak into the house as a gas, and rapidly decay into particulates that can get lodged in the occupants’ lungs.  It can also be found in water.  It is much worse for smokers to breathe radon gases than non-smokers, but that is true of many things!  Certainly not every house has radon issues, and it can be tested and it can be reduced to acceptable levels.  And just because your neighbors’ house has a radon problem it doesn’t mean that yours does.

Humidity is another significant pollutant for a wide variety of reasons.  Relative Humidity (RH) is indicative of the amount of moisture a volume of air can hold at a certain temperature.  Warmer air can hold more moisture than cooler air.  As the temperature of the air rises, its RH goes down.  That’s why cold winter air drawn into a house makes the air in the house drier.  Cold air in a closet has higher relative humidity and mold grows on the cooler surfaces.  RH is not the easiest thing to visualize, but we can certainly feel it.  “It’s not the heat.  It’s the humidity!”  The dew point is the temperature of a surface that will cause moisture to condense.  As the dew point rises in warm weather, our discomfort increases.  When the dew point is only a few degrees below the outside temperature, it is almost hard to breathe.  It is interesting to note that there are microclimates all around us.  The air around a glass of ice water can be cooler and at the dew point and moisture droplets form on the sides of the glass.  This is similar to the microclimate convective loops in insulation gaps and on the surface of walls.  All this stuff is going on around you.  Right now!  And you thought things were just sitting there!

Just to be consistent, we measure relative humidity with a device called a hygrometer.  A humidistat is a control that turns something on when the humidity goes down.  A dehumidistat is a control that turns something on when the humidity goes up.

Next time: The Skeleton!


Basement Dehumidifiers

September 11, 2012

Basement Dehumidifier

Dehumidifiers use a lot of power, in the range of 600 to 850 watts.  If it’s running 24/day, 365 days a year that’s 5,256 to 7,446 kWh per year or about $950 to $1,200 per year at eighteen cents per kWh.  That’s like $100 per month!  But wait, you say, they don’t run 24/365.  They do if the homeowner has cranked the control all the way to Continuous or doesn’t know how to set it.  I have been in people’s homes where I have saved them about half their electricity bill by simply turning down the dehumidifier.

I put a data logger down in my basement this summer when it was really hot, humid nasty outside, running with an outdoor dew point above 70 F.  The temperature in the basement averaged about 70 F and relative humidity averaged about 70% RH.  The dew point cruised at about 61 F.  My data logger was recording the air temperature, humidity and dew point.  That doesn’t mean that there weren’t surfaces in the basement that weren’t below 61 F.  Most of the mass of the basement has been there long enough to reach an even temperature, however.  So there may be dark, damp corners, but for the most part, the entire basement and all the stuff in the basement was above the dew point.

Many of the new IR cameras have a dew point screen that can be used to figure this out.  Or you could put in a data logger or hygrometer and figure it out.  There are so many dehumidifiers running in so many places that we could make a major impact on energy consumption just be getting them set up and working properly.  (There is a nice little dew point calculator at: .)  There are a bunch of places that sell hygrometers that will provide the temperature and humidity.  You can plug those numbers into this calculator and get the dew point.

The dehumidistat controls have vague settings from OFF to NORMAL to

Dehumidifier Control Panel

DRYEST to CONTINUOUS.  What does NORMAL mean?  There is a difference in using the dehumidifier to maintain a comfortable humidity in the living space and the right humidity to keep mold from growing in the basement.  For the basement application, the dehumidifier should be set to the lowest possible setting to meet the need.  It should be set so that the RH is below the dew point.  It should definitely be cycling on and off.

Many of the product performance numbers are based on operation at 80 F and 60% RH which is a pretty high temperature for a typical basement (or even a house).  Some of the manufacturers rate their dehumidifiers at 100% RH which is not a condition you would ever want to see in a basement!  One measure of the efficiency of these machines is how many pints (Energy Star rates them in Liters) it can remove per kWh.  If you take the stated Water Removal Capacity (in pints) and divide it by 24, divide that by power consumption in watts and multiply the whole thing by 1000, you’ll get the pints per kWh.  In the handful of units that I looked at they ran from a low of 3.47 (1.8 L/kWh) to 6.49 (3.07 L/kWh).  There is an interesting little closet sized unit that came in at 10.65 (5.04 L/kWh)!  Something seems a bit off with that one.

Why is the dehumidifier in the basement?  If it is to keep the mildew off the suitcases stored in there, it just has to keep the RH low enough to prevent condensation.  If it is to remove standing moisture in the basement, then you probably need a pump instead of a dehumidifier!  If the house having an energy audit has a dehumidifier, it should be included in the audit.  It is more of an energy load than a whole lot of light bulbs.