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.

Help! The ceiling leaks but the roof doesn’t?

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It was very cold, -20-30 C (or well below zero F) for a few weeks, but the deep freeze has ended, overnight it warmed up to well above freezing, everything is melting.  And there is this huge new water stain on the ceiling…  If this is your house, keep reading.

Here are some clues.  Your house has a humidifier and you use it, you do a lot of cooking, there are more than three people living in the house, you have a lot of house plants, someone, or maybe more than one someone, likes their long, hot, morning showers, and maybe forgets to use the bathroom fan, or maybe there is no bathroom fan.  Maybe you live in a older house with new insulation, or maybe your house has a cathedral ceiling.

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Frost inside attic hatch

 

The picture above was taken on a very cold day notice the ice (frost) built up inside the attic hatch opening.

The next picture, from another house was taken a few days after a big melt. This was an older house with upgraded insulation stuffed into the eaves, blocking ventilation.  A brand new rotary ventilator was spinning merrily on top of two year old shingles.  Insulation and rafters were very wet, and there were indications of mold growth in the attic.  Water was leaking everywhere.

wetinsulationandrafters

 

What is happening?
Air from inside the house leaked into the attic.  Warm inside air holds more moisture (humidity) than cold air. When the inside air enters the freezing attic the moisture condenses as thick frost. Because the frost does not evaporate readily, it builds up like the snow in your yard. The more inside air leaking into the attic, and the longer and greater the cold spell, the greater the build up of ice. If it warms up suddenly, the ice melts, there is too much water to evaporate, so it runs down, if it can collect somewhere, or it finds an opening, you have your leak, and a water stain.  Water may even run down the back (inside) of sloped roof sheathing and rafters and trickle into the walls.

If the air inside your house had been dryer, the moisture would have been absorbed by the dry air inside the attic before it could condense. If the attic was warmer it would also be drier because the air in your attic came from outdoors and able to hold more moisture, the leaked humid inside air might have dried or been absorbed  before there was enough of it to leak. If the ceiling and vapor barrier were intact the inside air would have stayed inside.

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Your indoor humidity is too high if you can see this

 

If you have this problem, there are a number of things you can do to prevent it. The first thing is to reduce the humidity inside the house. In all the cases above, the humidity indoors was over 30%. Even though 30% is recommended for comfort and even more for fine wood furniture or hardwood floors, it is too high for very cold winters. If you can see condensation on your windows, your humidity is too high.

Use your exhaust fans, you should have a kitchen exhaust to outdoors if you do a lot of cooking, you should have a bathroom fan in every bathroom that is used for showering. If you have no fans, you should open a door or window (this may be tough – be strong :-)) If these methods do not get indoor humidity below 30% you may need a de-humidifier.

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Eaves are blocked by insulation

 

Check the attic for adequate ventilation.   A well ventilated attic is a healthy attic.  If your house has upgraded insulation, it may not have been properly installed.  Air needs to be able to flow in from the eaves and out the ventilators on the roof.  Mixing static and rotary (turbine) ventilators is a bad idea, use one or the other.  A rotary ventilator can ‘short circuit’ attic ventilation by drawing air out of a nearby static ventilator instead of from the eaves.  Many pros only recommend static ventilators, rotary ventilators sometimes work too well, drawing air into the attic from inside the house.

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A well ventilated attic is a dry attic

 

Check the ductwork inside the attic, in Canada the only duct work normally found in attics are exhaust ducts from the bath and kitchen fans. All ductwork in unheated attics should be insulated. Straight pipe is better than flex, and uninsulated white plastic dryer vent is not appropriate for bath exhausts. All exhausts must be vented outside through the roof, not inside the attic. Exhaust ducts should be as short as possible. It is not difficult to install a ‘gooseneck’ for an exhaust duct on a normal asphalt shingle roof, there is no need to run duct from one side of the attic to the other.

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Air is leaking through the gap between the electrical octagon box and the drywall ceiling

 

You also need to prevent air from inside the house leaking inside your attic. The picture above shows a badly sealed light fixture in a cathedral ceiling, it has allowed air to leak into the attic space as well as  water back through the ceiling. Air may also be able to leak through the wire opening (knockouts) (circled). The area between the fixture box and ceiling should be caulked so that air cannot leak into the attic. A small amount of foam sealant at box openings will seal it. (Do not fill the box with foam, the electrical wires could overheat and cause a fire.). All openings in the ceiling between house and attic should be checked and sealed if necessary, including the exhaust fan openings.

New homes have a heavy (6 mil) plastic sheet vapor barrier between the unheated attic space and exterior walls. The sheets are taped where they are joined, and molded  plastic coverings for electrical fixtures are also taped into the vapor barrier. Older homes built between the 1960’s and 1990’s used lighter plastic (3 mil), lapped joints instead of taped joints, and no covers for the fixtures. Older yet homes may have lapped building paper under the plaster, or nothing at all. Whatever you may or may not have, it is not necessary to remove your ceilings and walls to upgrade your vapor barrier. Vapor barrier paint applied to exterior walls and ceilings will work just as well or better.

Cathedral ceilings can be a problem because they may not have any ventilation and their attic, if they have one, often cannot be accessed. If you have a cathedral ceiling it is particularly important that all ceiling penetrations are well sealed, and if necessary, a vapor barrier paint is applied.

And don’t forget to weatherstrip the attic hatch!

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Thermal image of air leak at the attic hatch