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Archive for the 'Air leakage' Category

August 29th, 2012
By Yves Carignan

Airtight homes keep in heat… and many other things.

At the beginning of my career, I had the privilege of working for a company specializing in residential ventilation called Venmar. The company is well-known in the industrial area of Drummondville and has developed and still developing products related to the treatment of air in residential and especially light commercial applications.

In the 90s, the homeowners wanted to find a solution to the obvious signs of excess moisture in the home; that being condensation on windows. Upon the arrival of the cool nights of autumn, each house with inadequate ventilation or excess humidity ended up with this issue. This occurred because we increased the airtightness of houses, trapping in air and therefore moisture which would normally “leak” out of the home. The captive humidity and cold outside turns this excess moisture into condensation on the windows of the home. The solution was to install a mechanical ventilation systems, such as those manufactured Venmar.

Several years later, breathing problems were becoming more and more prevalent and we put the blame on industrial pollution and the poor quality of the air were breathing outside. But for some time, we also noticed that the air in our homes is often 10 times more polluted than outdoor air! Why? Due to of all products used in construction; cements and other binders, paints, solvents, etc.

A U.S. study by Perkins + Will for the National Institutes of Health lists 374 pollutants, directly linked to lung disease, specifically Asthma in this study.

I leave you to read the study and even if I am not paid to tell you, please remember that the ventilation in your home is the best tool to get rid of these indoor pollutants!

November 3rd, 2011
By Vivian Martin

In our energy efficiency series of articles featured each Thursday, we provide strategies or information on how to make your new home energy efficient and comfortable. 

How leaky is your house? The only way to know whether your home is leaky or tight is to measure its air leakage rate with a blower door. By measuring the airflow of a fan that depressurizes a house to a standard pressure difference, a technician can determine just how leaky your home is. The photo shows a Minneapolis blower door from The Energy Conservatory.

Leaky homes are hard to heat and hard to cool. The only way to know whether your home is leaky or tight is to measure its air leakage rate with a blower door. A blower door is a tool that depressurizes a house; this depressurization exaggerates the home’s air leaks, making the leaks easier to measure and locate.

An energy-efficient house must be as airtight as possible. Many older U.S. homes are so leaky that a third to a half of the home’s heat loss comes from air leaks.

There is no such thing as a house that is too tight. However, it’s also true that there is no such a thing as an airtight house. Every house leaks, and that’s why we perform blower-door tests — to measure a building’s leakage rate.

Who needs a blower door?
Blower-door testing is useful for both new construction and existing homes. By testing a new home, a builder:

  • Can determine whether a certain airtightness target — for example, the Passivhaus airtightness standard — has been met;
  • Can document airtightness levels needed to qualify for certain home labeling programs, including Energy Star;
  • Can do a better job calculating heat loss and heat gain the next time he or she builds a similar house;
  • Can brag about the home’s airtightness to prospective homebuyers or drinking buddies.

If you’re building a new home, the best time to conduct a blower-door test is after the home is insulated but before the drywall is hung. If the test reveals major problems, the leaks will be easier to fix at that point than later on.

Want to learn more about the origin of the blower door test and where leaks are typically found? Read the full article here…

Each Thursday, we will feature a blog entry about energy efficient new homes, covering a range of topics from building innovations to ratings systems to “score” your home’s efficiency. Subscribe to theDrummondHousePlans blog to make sure you get the latest news on how to make your new or renovated home energy efficient.


October 27th, 2011
By Vivian Martin

In our energy efficiency series of articles featured each Thursday, we provide strategies or information on how to make your new home energy efficient and comfortable. 

Choosing an energy-efficient upgrade to your home includes decisions of conscience and return on investment. This handy graphic illustrates some optional upgrades, the cost of installation and potential energy savings.

(Click on graphic to enlarge)

Home Solar Power Discounts – One Block Off the Grid

Each Thursday, we will feature a blog entry about energy efficient new homes, covering a range of topics from building innovations to ratings systems to “score” your home’s efficiency. Subscribe to theDrummondHousePlans blog to make sure you get the latest news on how to make your new or renovated home energy efficient.


October 20th, 2011
By Vivian Martin

In our energy efficiency series of articles featured each Thursday, we provide strategies or information on how to make your new home energy efficient and comfortable. 

Much as one is more than the sum of their arms, legs, heart, and brain, so too is a house more than the sum of its parts. Everything is connected in both “systems,” and often in unexpected ways!

Having a dark roof will make air conditioning bills higher. Putting in a beefier kitchen exhaust fan can starve a distant water heater of air and cause dangerous pollutants to flow down (rather than up) the flu or make a fireplace dump smoke into the living room.

Loosely installed wall insulation settles over time, causing heat losses. Source: Home Energy magazine (January/February 2010)

There are often tell-tale signs when a home is not properly acting like the system it was intended to be. For example, ice dams are evidence of excessive heat loss, which make pretty icicles on the eve but can cause severe roof damage and danger on the ground. Moisture damage or bad indoor air quality are usually dead give-aways of some deeper problem (or multiple problems!).

The art of bringing a home back into “balance” frequently involves finding sources of air leakage. Often, an important (but out of sight) location of leaks is in the heating and cooling ducts. Providing enough air for combustion equipment like furnaces, water heaters, and gas dryers is also crucial. Tools like blower doors can be used in worst-case tests to see how the home system performs when stressed.

The Home Energy Saver “Hall of Shame” gallery shows the kinds of problems discovered by looking at the home as a system.

The story of a home-as-system is also told through the many benefits (in addition to energy savings) that can be had by fixing performance problems. These take the form of a quieter living environment, higher comfort, and elimination of safety hazards.

Read original article and access related links here…

Each Thursday, we will feature a blog entry about energy efficient new homes, covering a range of topics from building innovations to ratings systems to “score” your home’s efficiency. Subscribe to theDrummondHousePlans blog to make sure you get the latest news on how to make your new or renovated home energy efficient.

July 13th, 2011
By Vivian Martin

When looking at a home as a system, protection from the elements is a goal. Water and moisture can cause a great deal of damage to a structure and knowing all of the plains of potential pathways help to minimize damage and keep your home healthy. An article from Building Green helps to explain the pathways of water ingress and prevention of moisture  to the home.

Water gets in through four pathways

Water moves in, on, and through buildings through the following four paths. I’ll go through these in order of magnitude–the most water is involved in the first path, and the least is involved in the fourth.

1) “Bulk” water: rain, runoff, and wind-driven water

Liquid or “bulk water”–rain, runoff, and other flows–is driven primarily by gravity but also by wind and pressure differences. Bulk water on the exterior of a building is managed by moving water down and off of the building, while site features move the water away from the building. A system of interconnected flashings, drainage planes or weather-resistive barriers, free-draining spaces, and claddings manage exterior bulk water. 

Inside the building, we manage bulk water by preventing or containing plumbing leaks and condensation. Collection trays or pans, sensor-driven shut-offs, and routine maintenance defend against interior bulk water problems. Sprinkler systems introduce bulk water inside of a building in the event of a fire, but in addition to their benefits in quickly dousing a fire, they often prevent much larger magnitudes of water from being hosed in by the fire department.

2) Capillary water

Capillary water moves under tension through porous building materials or narrow channels between building materials that act like tubes. The porous nature of many building materials, and the incredible cohesion and adhesion of water means that liquid water can move against the force of gravity quite effectively.

The primary defenses against capillary water movement are capillary breaks in appropriate locations, such as the between the foundation and moisture-sensitive materials sitting on it. Capillary breaks are non-porous materials–such as sheet metal, impermeable membranes, closed-cell foams or plastics–or free-draining air spaces (sometimes referred to as rainscreen), generally 3/8″ (10 mm) or larger.

3) Air-transported moisture

Air-transported moisture is the vapor content of air as it leaks out of or into a building. Air leakage is driven by a combination of holes through the building envelope and one of three driving forces: wind, stack effect, or mechanically induced pressure differences (fans) between the inside and outside of the building.

The primary concern (other than the heat content of the escaping or entering air) of moisture-laden leaking air occurs when it is accompanied by a temperature drop, increasing condensation potential. For example, warm, humid air from a shower in the cold winter months can leak around the bathroom light fixture into the attic, condensing on the roof sheathing–eventually leading to rot.

We manage air-transported moisture with a continuous air barrier in the building envelope, built with interconnected air-impermeable sheet goods, caulks, sealants, and spray foams. To be completely effective, air barriers should be in contact with thermal barriers (insulation).

4) Vapor diffusion

Vapor diffusion is the movement of water as a gas according to relative humidity gradients or differences in vapor pressure. Water vapor moves from areas of high concentration to areas of low concentration.

You often hear about use of vapor barriers to restrict vapor movement in buildings, but anything that slows vapor movement is a double-edged sword: while we may want to control the movement of vapor into a building assembly, we should be much more interested in how the vapor permeability of individual building materials and assemblies affect the movement of vapor out of building assemblies. While building assemblies can get wet by all four forms of water movement, once water gets in, the main way it can get out is by diffusion, so it pays to make sure that assemblies can dry through diffusion in one or more directions.

Quite often the vapor drive of water into building assemblies is climate- and season-related: vapor drive is from the inside of heated buildings in the winter and from the outside of cooled buildings during the summer. We need to balance the restriction of this climate- and season-based vapor movement into building assemblies with the allowance for drying of the same assemblies. We do this by conducting a vapor profile analysis or hygrothermal (humidity plus temperature) modeling.

Water management and insulation

That’s a lot to digest, but it helps to understand these fundamentals when you are thinking about adding insulation to your building. Insulation restricts the flow of heat, which in turn reduces ability of building assemblies to dry out when wet. Lots of old buildings don’t manage moisture very well, but that’s not a problem for them because they are so poorly insulated that they dry out easily. Adding insulation to older buildings is a good idea for a lot of reasons, but we must think about moisture at the same time.

Read full original article here…

 



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