Mechanical systems can cause penetrations within the building envelope, it is important to ensure all penetrations are insulated properly. If you make a building tighter it will have an effect on the heating/cooling systems. Making a building more air tight can help create the conditions that cause combustion gases to back draft from spillage susceptible heating systems

When a home is built, the mechanical systems are sized and selected based upon the current state of the home. When upgrades are completed to a home, they often change the homes heat loss, moisture levels, air flow, etc. The mechanical systems may need to be upgraded or adjusted to meet the needs of the upgraded home.

Some examples of signs that the upgrades completed to a home are contributing to problems are provided below:

• Increased condensation on the windows
• An increase in noticeable odors due to lack of air exchange
• Short cycling of the heating system, which makes the system less efficient

Spill Susceptible Mechanical Systems

Above are some examples of combustion appliances you may find in a home. Not all of these are spillage susceptible. Sealed combustion units like the furnace at top right are safer than naturally aspirated furnaces and boilers like that shown at top left.

Heating/Cooling System Sizing

Heating/cooling systems are sized based on calculations that take into consideration these three factors:

1. The R-value of the building materials used
2. The area of the building/space
3. The indoor and outdoor temperatures (Delta T)

Equipment sized according to proper heat gain/heat loss calculations will always work more efficiently and provide a higher level of comfort.

Over sizing is a real issue. Over sized systems cost more, are less efficient, provide less humidity control, and have shorter life spans due to excessive on-off cycling.

Heating Load

Heating Load is The amount of heat required to keep a building at a specified temperature during the heating season, regardless of outside temperature.

Design Heat Loss is The total heat loss from a house per hour when the outside temperature is at the winter outdoor design temperature and the inside temperature is at the winter indoor design temperature.

Design Heating Loads

If a building is being insulated that has never been heated before, and the intention is for the building to be used for residential occupancy during the winter months, Building Code requires that a heating system be designed and installed.

This should be mentioned to your client as it may change the scope and schedule of the work to be performed.

Refer to NBC 9.33.2.1 or OBC 9.33.2.1 for details.

NBC 9.33.3.1 states that a building must be able to maintain certain indoor air temperatures with the outdoors at the outside winter design temperature.

1. 22°C in all living spaces,
2. 18°C in unfinished basements
3. 18°C in common services rooms , ancillary spaces and exits in houses with a secondary suite
4. 15°C in heated crawl spaces

OBC 9.33.3.1 lists temperatures as well.

1. 22°C in all living spaces,
2. 22°C in unfinished basements, and
3. 15°C in heated crawl spaces

Cooling Load

Cooling load is The amount of cooling required to keep a building at a specified temperature during the cooling season, regardless of outside temperature.