New Homes, why it’s not easy being green

New homes and homes upgraded for energy efficiency in cold climates are more likely to have mold and moisture problems than older ‘inefficient’ homes.  Building codes that have incorporated energy efficiency requirements may have done so at the expense of maintaining healthy indoor air, especially when so little is being done to educate home owners on how a modern home works.  If the installed ventilation systems in new homes are not used or maintained, air can get stale.  Stale air has higher humidity and possibly unhealthy or even hazardous gases and vapors, the result of people pets and plants breathing and exhaling water vapor and carbon monoxide, showering, bathing and cooking.  Small amounts of potentially cancer causing ground gases like Radon may be seeping in through basements with inadequate or unused ventilation, building materials, paints, adhesives, carpets, flooring, cabinets may off-gas various solvents or water vapor as they age, which could be removed by a good ventilation system, provided people use it.

In places where outdoor temperatures remain at or below -18 C, or zero Fahrenheit, like Edmonton, home energy efficiency means reducing heat loss.  Heat is lost from homes in two major ways, heat energy transfering from hot to cold through exposed walls, windows, doors and ceilings, and through the loss of heated air replaced by outside cold air that has to be heated.  A small amount of heat energy is also lost through radiation, but that is negligible.

A house in winter is a box full of hot air, if left it will cool, the same as the cup of Starbucks left sitting. As indoor air comes in contact with walls, windows, etc., heat moves from the warm air to the cold surfaces.  Exterior walls windows and doors in turn pass the heat to outdoor air.  Left long enough all the indoor air and all surfaces in contact with it will reach the same temperature, whatever it is outside, (which is warmed infinitesimally, but not so the squirrels would notice).  The rate of cooling can be slowed by insulation the same as a not so green foam coffee cup.

Insulation in homes is mostly fiberglass batts, a type of fiberglass blanket installed between the studs, (the 2by sticks that make up exterior walls), and loose fiberglass blown into the attic.  Fiberglass is very thin strands of glass. Put your hand on a window when it is cold out, glass is not a very good insulator, the actual insulation is provided by trapped air, which is a very good insulator, the fiberglass just keeps the air from moving (the same is true for that foam cup, trapped air is actually doing the insulation).  Fiberglass and its cousins, mineral wool, cellulose, wood chips etc., have a insulation rating of about R3.5 per inch, (excuse the imperial measurement, but that is what most people are familiar with).  So, an ordinary house with 2X4 walls will have walls that are approximately R12, and if they have about 12 inches (300 mm ) of attic insulation, for a ceiling rated at R40.  With the exception of the R40 attic insulation, it is also pretty much the way we have been insulating homes in Alberta for 100 years.

New homes have different attics than older homes.  Older homes made roofs and attics using rafters and joists, 2by lumber that had to sized deeper for the loads it was expected to carry, a typical joist depth (the lumber the ceiling was fastened to) was 6 inches (150 mm), filled with wood chips for an R rating of about 19.

New homes are built with trusses instead of rafters and joists.  Trusses are engineer designed triangles of thin lumber, like those toothpick bridges they made you build in elementary school.  All those triangles make access to attics difficult, storing stuff is no longer an option, but otherwise useless attics are easy and tempting to pack with insulation.

So insulation wise, a new home does not necessarily have much more insulation in the walls than great granny’s Edmonton* 1920 new house had, but do have more attic insulation over the top floor ceiling.   This is all good, great granny’s builder was no dummy, he knew how to build a house for an Edmonton winter, but don’t automatically assume that today’s new home construction is advanced as say, the way today’s new cars are made over  cars made 100 years ago.

A dirty little secret is that home builders don’t like to spend money on stuff that can’t be seen, because Mr. or Ms. Newhomebuyer aren’t eager to hand over more money on stuff they can’t see.  It is usually easier for a new home sales person to convince buyers to upgrade to granite counter tops than triple glazed windows and energy efficient ventilation.  Another dirty little secret is that even though attic insulation has gone from R19 in 1920 to R40 in 2016, that does not make much difference in heat loss, but it does sound good.

A ceiling is a horizontal wall with no windows or doors.  Heat loss happens over exposed cold surfaces, a function of area, consider a 2000 square foot two story square house, each story 9 feet high, and four outside walls 31 feet wide, total exposed wall area is 31 X 9 X 4 X 2 stories, or 2200 square feet of exposed no better than R12 wall vs 31 X 31, 1000 square feet of ceiling exposed not quite to the exterior, but to an unheated attic that still has a roof to provide a bit of weather protection.

Windows and doors have much lower R ratings, no better than R 3 for triple glazed windows, not quite R2 for double glazed or Great Granny’s double storm windows that had to be taken down and stored in the spring.  Windows, old or new provide a fraction of the insulation provided by an ordinary insulated 2X4 wall with siding.  A new home probably has more window area than Great Granny’s as well so that 2200 square feet of wall will add up to a lot less than R12 overall when windows and door area is factored in.   So, by all means insulate the heck out of the attic, but don’t expect a great improvement in heat loss.

One thing that has changed a lot since Great Granny moved into her new home is dealing with the second major source of heat loss, air leakage.   Older homes could be pretty drafty, especially around windows and doors or any other openings such as electrical outlets in exposed walls and ceilings.  Air leaking out is replaced by unheated air leaking back in which will need to be heated.

Home builders have been dealing with air leakage for about 50 years, as plastic films used for air barriers became cheap and available.  Sealing and caulking openings, like windows and doors when they are installed or replaced is fairly easy to do, like stuffing the attic with more insulation. As building codes change, requirements for air sealing are tougher, enabling those who write codes to pat themselves on the back for being green and saving energy at no cost (to the code writers).

New homes are very tight, if built right, very little air can get in or out.  If you are thinking this is good stuff, ask any kid what happens when you put a living frog in a screw top jam jar with no air holes.    We need fresh air, our homes need fresh air, and as homes got tighter, things needed to be done to ensure that a home received fresh air.

The basic requirement as of this writing is a fresh air intake duct and mechanical ventilation (fans) to bring in the fresh and remove stale air.  The most common way Edmonton builders comply to ventilation code is to insert a fresh air intake into the forced air heating system return air duct, so that whenever the air handler (furnace) fan is running, fresh air is brought in by the furnace and distributed through the heating duct system.  A ventilation switch operates an exhaust fan and the furnace fan at the same time when it switched on.  Homes that do not have forced air heating need to have an exhaust and intake fan operated by the ventilation switch. An HRV (heat recovery ventilator) is a self contained unit that can take care of bringing air and exhausting stale air, with the added benefit of using exhausted air to warm incoming air with a heat exchanger.   The most basic systems are operated by a switch which require the occupants to decide whether or not they need fresh air.  More sophisticated systems use automated programmable controls to ensure that a home’s air is exchanged on a regular basis.  The Canadian Home and Mortgage Corporation (CMHC) recommends an indoor air change every 3 hours.

Most homes built before 2010 in Alberta had an ‘automated’ air exchange system operated by the chimney.  Most homes in Alberta are still heated by fire (just like those jolly old caves used our great great great… and on so great grannies).  For the last 70 years the fire has been natural gas burned in a furnace, previously  we burned coal, wood and before that, flaming dried buffalo poop kept tipis nice and toasty.

A fire requires air to burn, it also produces smoke if you are burning coal, wood or buffalo droppings, but even clean burning natural gas produces water vapor and carbon dioxide, which has to be gotten rid of.  A chimney or an opening up high allows the hot products of combustion we don’t want to naturally rise up and out, carrying warm air with it, which was replaced by incoming cold air, leaking in from everywhere at first, and for the last few decades by combustion air intake ducts. By placing the furnace, chimney, and combustion air duct in the same room, usually the basement or part of it, the incoming combustion air also mixed with the air in the house, and indoor heated air went up the chimney.

The drive to save energy and make homes and appliances more efficient resulted in redesigned for energy efficiency furnaces that use no inside air, Today’s high efficiency gas furnace, the only kind available, draws all of its air for combustion from outdoors, extracts most of the heat from the exhaust before blowing it back outside through a plastic vent pipe at the side of the house instead of a chimney, so no more heated air flying out chimneys and no more automated ventilation.

New homes have an adequate ventilation systems, provided people use them.  You may be saving a few pennies on your gas bill by keeping fresh air out of your house, but the possible health costs or damage to your home will give a 21st Century meaning to the phrase penny wise, pound foolish.  It is fairly easy to keep indoor air fresh, use the systems that are installed in your home, make sure that the air intakes are free to draw in the kind of air you would prefer to breathe, and make a practice of  opening doors and windows every so often to let some fresh air in.

*Not necessarily true for regions that did not experience extremely cold winter temperatures.

Humidifiers, threat or menace?

Based on my inspections the humidifier may be the most neglected and unloved appliance in your home. Probably nine out of ten humidifiers I inspect are a mess.

Humidifiers are used in winter time to add moisture to dry air during heating season.  A humidifier mounted on a furnace uses water from a water line to add moisture to the air heated by the furnace, which is then distributed throughout the house using the hot air ducts. There are three basic types, evaporative, drum and flow through. The simplest is the evaporative type, a hole is cut in the hot air plenum of the furnace and the humidifier, consisting of a water reservoir and some metal plates, is installed in the hole.

Evaporative humidifiers
Evaporative humidifiers

Heated air absorbs the water as it passes by. They are simple, often have no controls other than a float or valve that maintains the water level. They are shut off by cutting off the water supply (which will work for any other humidifier as well).

The drum type has a hollow cylinder covered with a water absorbing foam driven by a small motor, the cylinder or drum rotates through a water reservoir with a float to control water level.

Drum type

There are automatic controls to turn the motor on and off, often there is a manual damper to close off the air passing through the humidifier, and the water shut off valve. The humidifier is mounted on either the hot air plenum or the return (cold air) plenum, there will be a short length of duct connecting the humidifier to the plenum that the humidifier is not mounted on. When the furnace fan is on air moves through the connecting duct from the supply to the return, passing through the humidifier and the rotating drum, picking up moisture as it passes through the humidifier, which then goes back through the furnace from the return side to the supply air to the house.

Flow through

A flow through humidifier is installed the same way as a drum type, on either plenum and with a duct to the other plenum but there is no drum or reservoir. A rectangular pad containing 40 mm thick metallic mesh is fed water from a valve above the pad, water is either picked up by the warm air passing through it or it flows back out through a plastic condensate line into a floor drain. Water flow is controlled by an automatic control called a humidistat.



The humidistat is an automatic control that is activated by sensing humidity, only releasing water onto the pad when it is needed.  There should also be a manual damper to shut off air flow through the humidifier.

When I inspect humidifiers, this is mostly what I see,


calcified evaportive type




Eeew! what is that? Calcified drum type
Calcified pad from flow through type
Rust on furnaces caused by overflowing humidifiers

When I find a badly maintained humidifier my recommendation in most cases is to remove or shut down the humidifier. Most homes in Edmonton don’t need one, for non Edmontonians, you probably don’t either, but don’t take my word for it 🙂 Edmonton has a humid continental climate, the outside design temperature is -32 C (the projected coldest two weeks of the year). What this means is that no one needs a humidifier in summer, and when the weather is cold inside humidity needs to be kept low to prevent condensation inside, which can lead to damaged building materials and mold.

So who needs a humidifier?

You have valuable, make that priceless, museum quality antiques made of wood, paper or textiles that will be damaged if they dry out. (yup you need a humidifier)

You have hardwood floors. (maybe) The bad news is that your floors will dry out even if you have a humidifier, if the floors are old hardwood, no need, they are already dried out, what you see is what you get, new floors will dry out too, that is what hardwood floors do, they will shrink as they dry out.

You have health problems related to dry air. (If your doctor says you need a humidifier, you need a humidifier)

You feel cold but the thermostat is set to a high temperature.  (Dry air will make you feel colder than humid air, you need to wear a sweater, you don’t need a humidifier)

You have a hygrometer, it is accurate, it reads less than 20%. (Your house may be too dry, extremely dry air can cause health problems, you may need a humidifier.)

You have an accurate hygrometer you are heating your house and the readings in your home are 40% or higher, condensation is forming on your windows. (You DO NOT need a humidifier, you need to turn it off if you have one, you may need a de-humidifier if you do not have a humidifier, or you have turned your humidifier off)

Turning off your humidifier

Turn off the water, turnoffwater
Close the damper, turnoffdamper

Turn off the humidistat turnoffhumidistat


If you must have a humidifier, the only kind I recommend are the flow through types, because they only release water when needed, when the furnace is running and the humidistat calls for more humidity. Flow through humidifier pads have to be checked regularly and replaced when they become calcified, usually once a year. The damper should be closed for the summer (the ‘off position may be labelled ‘summer’), the humidistat set to zero or off in summer, the water does not necessarily need to be turned off for a flow through, but it won’t hurt to do so.

If you are still using an evaporative or drum type, the water should be turned off for summer and the float and reservoir taken out and cleaned, and put back dry. Drums or the drum media should be replaced when calcified. You should also be measuring the relative humidity in your home in winter, never allow it to reach more than 30%. If you see condensation on windows, especially bedroom and living rooms windows, your inside humidity is too high, and you need to turn down or turn off your humidifier.

If you are installing a humidifier, the best place to mount it is on the return air duct, it can be mounted on either return or supply, except evaporative types which must always be mounted on the supply or hot air plenum. Mounting the humidifier on the return plenum will minimize (but not prevent) damage to the furnace should the water line leak or the humidifier overflow, so check your humidifier often.

Something you might not know about your basement

Inside basement wall thermal image. The area outlined in the box is the same as the outlined area of the exterior image
Thermal image of uninsulated basement wall from outside. The area outlined by the box is the same as the area outlined in the interior thermal image


Did you know that your 8 inch (200 mm) of concrete basement wall has about the same insulation value as a single pane of glass? Take a look at the thermal images of a 1951 bungalow with insulated basement walls. Comparing the temperature of the concrete and the windows, we can see that the windows are actually slightly cooler, the windows are not transmitting as much heat as the concrete. That is because they are double windows, with an R value of about 3, compared to the the concrete’s value of about 1. The upper part of the house is 2X4 studs sheathed with lumber coated with stucco and rock wool insulation between the studs, with an R value of about 12.  The ambient outside air temperature was about -1 outside, and the indoor temperature in the basement about 19.

New homes typically have 6 inches, or 150 mm of fiberglass insulation on the basement walls, but not that long ago few homes were built with uninsulated basement walls. In the 1970’s builders insulated the part of the basement that was exposed, based on the theory that the soil and ground cover provided adequate insulation for the concrete below grade. While it is true that soil temperatures are generally not as cold in winter as the outside air, it is also true that soil temperatures are almost always considerably less than what is considered a normal indoor temperature. This can be seen in the interior thermal image, the warmer appearing wall on the left is drywall fastened to 2X3 studs, with an approximately 2.5 inch or 35 mm air gap.  The drywall temperature is about 18 C, the exposed concrete 12 C and the concrete below grade is between 13 and 14 C.

In Edmonton soil temperatures are about 10 C below the frost line (about 6 feet or 186 mm below the surface). It is always a good idea to insulate your basement, as your basement is inside the building envelope, or the inside of your house that is heated by your furnace. Allowing any part of your house inside the building envelope to get cold can lead to excessive humidity in cold areas, condensation and possible mold growth.  If you would like East Side to inspect your home and basement, call 780 477 2666 and make an appointment.