3rd step - Insulation and sealing

Insulation and sealing

Sealing (air & water)

Tightness is essential. However, if we often talk about building insulation, we talk less about waterproofing. And it is often also more neglected. Indeed, waterproofing takes time and thoroughness. In addition, the insulation is more tangible and more visible: a very thick wall can be seen; not a perfect seal. Finally, there is no performance obligation in the building code at this time. This is why it is not a common practice in the construction industry.

But then, why is this so important? The tightness is felt and measured. By limiting water and air infiltration, we limit rot and mold in our envelope. Durability, air quality, comfort: three big advantages.

For an optimal seal, here are some tips that we use:


  • Seal the vapor barriers of walls and ceilings with acoustic sealant at all junctions, and secure with wood furring to crush the sealant
  • Seal the edges of the floors with sprayed polyurethane
  • Seal window towers with low-expansion polyurethane foam
  • Install double furring to pass the electrical wiring without perforating the vapor barrier

Water tightness

The exterior cladding is a first level of protection which has its limitations.

Careful work must be carried out behind the exterior cladding to ensure a second level of protection, with for example:

  • Overlap of the weather barrier
  • Protection of window jambs
  • Window membrane
  • Flashings

Weather barrier, vapor barrier, air barrier, what is it?

These are three technical terms that we often come across when we are interested in construction. They are indeed fundamental for the waterproofing of the building:

  • The weather barrier blocks all possible water infiltration to the outside, it prevents rain from entering the envelope. For this, waterproof seals, effective and well-made flashings are required.
  • The air barrier must be well sealed to prevent air infiltration into the interior of the house. It allows you to have a home without drafts, comfortable.
  • The vapor barrier is placed on the warm side of the envelope. Its role is to protect the insulation from excessive moisture that there may be in the house.

The infiltrometry test

The infiltrometry test is the step in determining the waterproofing rate of a construction.

Basically, it consists of placing a large fan in one of the building's doors, while closing all openings (doors, windows, fireplace, etc.). By turning on the exhaust fan, the house is depressurized. The air is therefore drawn in through the holes in the house and these potential air infiltrations, no matter how small, are then noticeable. Particular attention is paid to the weak points of the envelope: junctions of walls, ceilings, floors, window frames and all perforations of the envelope. Depending on the size of the house and therefore its air volume, the infiltrometry test can determine the air change per hour (ACH) of the tested building.

Belvedair, ensures the quality of the waterproofing in each of its houses and this is moreover the role of Novoclimat certification, which we will discuss in the seventh step: Certifications. It will be understood that waterproofing is crucial for energy efficiency and the preservation of the building, therefore for comfort and for health.

Optimal insulation

What is the optimal insulation?

We often have an attachment to walls and ceilings which generally represent between 10 and 20% of heat loss. However, we can see from the graph below, that the main heat losses are actually played out mainly elsewhere.

What is the best wall cut?

For us, a good wall cut should be simple to make, should use readily available or easily accessible materials, and have a level of insulation that is both cost effective and of course comfortable.

Many people ask themselves: what is the best wall cut? Big question ... We can summarize the answer by saying that it is important to have good insulation, but above all to block thermal bridges: we want the most continuous insulation possible. Preventing the creation of thermal bridges is, like sealing a building, a way to "tie up our big coat".

Some of the materials we use most today are cellulose, rock wool and expanded polystyrene (blown in air). These materials are easy to access, easy to process and contain, either recycled or preferable for the environment. Polyurethane, which has an unfavorable ecological balance, is to be used only where it cannot be replaced as effectively by something else, for example around windows.


The R factor is a symbol that represents the thermal resistance of materials, it translates the power of the insulation. The higher the R factor of a material, the more effective it is as an insulator. It is customary to add the R-values of the component materials, for example: a section of a wall, in order to give a clear indication of the insulating power of this one. The goal with insulation is to bet where it makes a difference.

For walls: we recommend R-30 and above. In a roof: R-60. Under the concrete slab: R-16 and for foundations, often neglected in insulation, you should aim for R-28. These degrees of insulation are much higher than what the Building Code requires. However, the goal also remains to bet where additional insulation is relevant. This is why, passing a certain stage, insulating the walls even more (for example) is no longer useful, it is necessary to concentrate where there is really heat losses (see the graph above): it is therefore necessary to work on doors and windows, on foundations, or on the heat recovery ventilation system.

The Windows

The basic principle

In a passive solar house, windows are considered to be solar collectors. They allow solar energy to be stored directly inside the building (same principle as in a greenhouse), but of course it is a question of further tempering the heat! Windows, and through them the sun, are the basis for heating a passive solar house.

Windows facing North, East and West have an energy balance in deficit over the cycle of one day. On the other hand, a window on the south side will have a positive energy balance.

The theory is therefore simple at first, but to work, it requires making judicious choices for the orientation & sizing of the windows, for the choice of glazing, framing and glass. And to think all for our climate!

Double or triple glazing?

In passive solar homes, the goal is to keep heat inside in the winter and keep it out in the summer. A wall section like ours has an insulation factor of R-33.5, counting only the insulation, without adding the coverings.

The insulating value of windows is much lower and it is therefore through windows that most of the energy losses occur. Windows typically account for 40-60% of a home's heat loss in winter.

Since you cannot build a house without windows, you will understand that the object of the game is to have the most efficient windows! We must therefore systematically turn to triple glazing.

The increase in the insulating value of triple-glazed versus double-glazed windows is almost double: either R-3.5 for double and R-7.1 for triple and its additional cost is only 10 to 15%. The effectiveness of the triple glazing will be appreciated on the south wall as on the others, as it also helps prevent overheating outside the heating period. And it's not sunny all year round!

In short, we will understand, triple glazing is required!


Energy performance should be the first criterion of choice, to guarantee comfort and lower energy consumption. ENERGY STAR® certification is a good indicator for sorting out the many choices of doors and windows on the market. This certification is also compulsory for doors and windows in Novoclimat houses.

"Administered in Canada by Natural Resources Canada (NRCan), the ENERGY STAR® certification program sets general and energy performance criteria that distinguish the most energy efficient products on the market. The program certifies 15 to 30% of the most energy efficient products , in many product categories: refrigerators, computers, washers, and of course doors, windows, and skylights. There is no need to recall the amplification of climate change and the reasons why the construction market is constantly increasing its prices. energy performance criteria. Excellence programs such as ENERGY STAR® are the main players. They pull the market up, and periodically increase their requirements to keep certified products at the top of the basket. ENERGY STAR requirements of today are those of the Building Codes of tomorrow." 
Source: Ecohabitation

We talked about triple glazing, but with what types of glass? For extremely high-performance windows, triple-glazed windows, with double Low-E film, will be preferred. In the jargon, we can also speak of Low-E glass. Low-E expressing the term "low emissivity".

This type of glazing is clear thermos glass, to which an invisible metallic layer has been added, which allows outside light to pass but which blocks heat radiation from inside the house.

The goal with this type of glazing is to reduce the building's energy consumption, in winter of course, but also in summer by reducing solar energy input and therefore air conditioning requirements.

To refine this, it is also necessary to know certain indicators:

  • the U factor expresses the amount of heat transferred through the window. The smaller this factor, the better the insulation. The most insulated windows are more comfortable, in addition to limiting condensation.
  • The Solar Heat Gain Coefficient (CGCS) expresses the amount of solar heat that the window lets in. The higher the CGCS, the more sunlight the window can penetrate.
  • The air leakage rate expresses the airtight performance of the window.
  • Finally, the energy efficiency (ER) summarizes the previous parameters in order to express the overall energy efficiency of the window.

For a choice of glazing, one can juggle between the U factor and the CGCS. It is possible, for example, to choose less insulated windows (lower U) but with better solar gain (higher CGCS). However, keep in mind that overheating is more difficult to control than comfort in cold weather. Therefore, we recommend instead to minimize the U factor (i.e. maximize the insulation of the window) and to some extent also minimize solar gains (minimize the CGCS coefficient). The passive solar house will only be more comfortable, in all seasons.

Argon is an inert, non-toxic gas, which acts as a thermal insulator. In other words, it serves as a filler between the panes, and advantageously replaces compressed air, because it is heavier and has better performance.

The alliance between Low-E and argon films provides excellent energy efficiency.

The waterproofing of a casement or awning window, with a crank in both cases, is to be preferred. When closing this type of window, the weatherstripping is properly crushed and seals the window. Sash or sliding windows, on the one hand weatherstripping on the one hand are not as effective, on the other hand, wear out much faster.

In terms of design, if desired, we can reproduce the style of sliding windows, more rustic, while technically opting for awning or casement windows.

The type of frames and the installation

For a window to be effective, its frame must also be effective and the installation must be done well!

For framing, many choices exist and each has its advantages and disadvantages. There are some in wood, PVC, aluminum, fiberglass, and hybrid models combining, for example, PVC and aluminum, wood and PVC…

At Belvedair, we generally (although not exclusively) do PVC or hybrid PVC / aluminum frames; by turning to the most efficient and Energy Star certified models. While these materials are not perfect (but none of the frames are), they have the advantage of being very durable (when choosing quality models), relatively inexpensive compared to other choices, and above all to provide excellent energy efficiency. It is this framework that has emerged as a winner in the life cycle analysis commissioned by the Conseil du Bâtiment Durable, the body that manages LEED certification.
Source: Life Cycle assessment case study of North American Residential Windows by James Salazar, B.Sc., The Georgia Institute of Technology, 2003

An extremely efficient window must be properly installed ...