Thermal Comfort Overview
Air Sealing Key Points
Thermal Comfort:
- Condition in which a building maintains a level of temperature and relative humidity where the occupant(s) are in a state of comfort
- The range of comfort for most occupants of a building is between 70 º F to 75º F at a relative humidity of 30%-50%
- To properly maintain thermal comfort, a building should have a complete building envelope, which consists of an air barrier in contact with insulation to reduce heat flow through the building
- Properly designed and installed heating and cooling systems can maintain thermal comfort during extreme and less moderate weather conditions
RATIONALE
Thermal comfort of occupants in a building can help reduce energy use. If occupants are not comfortable, they may repeatedly adjust the thermostat to turn on the heating and cooling system, which uses more energy. But if a building is properly designed and built with occupant thermal comfort in mind, it will use less energy in heating and cooling and also result in fewer maintenance calls to address comfort issues. An additional benefit of thermal improvements to a building is that they can reduce the size of the heating and cooling system needed to maintain thermal comfort, often reducing construction or remodeling costs.
SUSTAINABILITY PRINCIPLES
Thermally sound buildings:
- Use less energy in heating and cooling by reducing heat flow through the building
- Reduce carbon footprint
- Prolong life of heating and cooling equipment if properly designed and installed
- Require less maintenance
- Improve durability of building
EFFORT REQUIRED
Improving the thermal envelope of a building is relatively inexpensive, but may require more attention to detail and require additional training and/or quality assurance measures.
- Most holes in the building envelope occur where penetrations are made for plumbing, electrical wiring, or mechanical chases. They must be sealed before drywall is installed.
- Proper installation of insulation to avoid gaps or compression may require training and quality assurance measures, but maximizes the effectiveness of the insulation.
- Permanently sealing ductwork with mastic duct sealant reduces leakage of conditioned air into unoccupied spaces and increases delivery of air to conditioned occupied spaces (Duct tape is not durable and is unacceptable in sealing duct work).
- Properly sizing the HVAC system may also require training and/or quality assurence to achieve an optimally designed system to improve thermal comfort. Hiring a commisioning agent is highly recommended.
- Attention to window and glazed door orientaions and overhangs over glass to reduce solar heat gain should be considered. Other alternatives are solar shade screens installed on the exterior of the windows that allow light to come in while reducing solar heat gain.
BENEFITS
The benefits of thermal comfort include:
- Increased occupant comfort
- Increased durability of building components
- Reduced energy costs
- Reduced carbon footprint
- Reduced building maintenance
- Improved indoor air quality with proper ventilation strategy
RISKS
While building an air-tight structure can reduce infiltration of outdoor air pollutants, it can also trap indoor air pollutants in the building. A tight building should install a proper ventilation system that helps control the source of air coming in and out of the building. Most ventilation strategies allow for filtration and conditioning of outdoor air before being distributed to the building in order to dilute indoor air pollutants.
ACTION AGENTS
Commissioning agents should be involved in the design process to help acheive a thermally sound building. Architects should also work with contractors in their design to make sure that drawings account for air sealing, insulation details, duct work layouts and selection of properly sized heating and cooling systems.
A commsioning agent can help ensure that contractors are trained on proper air sealing and insulation techniques:
- Plumbing and electrical trades should be trained on properly sealing penetrations in the building.
- HVAC trades should be trained on duct sealing and correctly sizing the HVAC system.
- Insulation workers should be trained on reducing insulation gaps and compression to maximize the effectiveness of insulation.
Builders should be trained in managing a project to help ensure these measures are followed, as well as hold contractors accountable to maintain a good thermal envelope. A builder will also benefit from the assistance of a third party technical assistant to verify the proper installation of building components to maximize thermal comfort.
COSTS
Additional costs for thermal comfort measures are minimal in comparison to the longer term costs of energy inefficiency or poor thermal comfort. With new construction, spending a bit more on the design phase will reduce costs down the road. The key is maintaining quality assurance throughout the construction phase to ensure that building components are installed properly. Spending this extra time to get it right the first time will have a quick payback in energy savings and comfort.
The related carbon generated from any given activity. For example: one mile of driving an average compact vehicle generates .6 pounds of carbon from the burning of gas. This does not count the embodied energy of the manufacture, maintenance and disposal of the car and nor the construction of the road and its maintenance.The quality of air inside a building space that affects the health and wellbeing of building occupants. The process of verifying and documenting that a building and all of its systems and assemblies are planned, designed, installed, tested, operated, and maintained to meet predetermined energy requirements.The ability or potential of a physical body to do work. The most common forms of energy are heat, light, mechanical (moving parts), and electrical.
