Thermal Resistance and Energy Efficiency (Insulation and Air Barrier)
OVERALL –Average for age of home – Most homes of this era have very ‘leaky’ construction that allows
considerable air movement through the building enclosure, which usually results in higher heating costs and
condensation potentials within the wall and attic assemblies. This home had parts of the dwelling with an observed
vapour barrier (attic over dinning room) and parts without (main attic). The thermal wall & attic insulation
requirements for the period of construction this dwelling was built in, were quite low compared to today’s
standards.
OBSERVATION:
- The exterior wall insulation was generally behind finished surfaces and not observed.
- The main attic insulation comprised of around 1” of compressed minneral fibre bats under an approximately 6
inch fiberglass batt. It is estimated that the combined thermal insulation value for the whole attic (takling into
account thermal bridging from structure, the lack of continous air barrier, and the ununiform application of the
insulation is around R9-12. Current best practices dictate around R40 for attic areas and by the summer of
2012, this is expected to climb again when a new building code revision is implemented.
- It is recommended that an energy audit be performed to determine if upgrading the attic insulation will result in
an acceptable payback period based on energy savings. Cellulose is a very cheap insulation material to add in
an attic and significant depths can be achived with realatively low costs. Usually the call out is the most
expense part of a insulation project. Asking for an extra 6” or even 12” of insulation is often very little extra
cost from the initial fee. Just make sure that baffles are installed (preferably in each rafter bay) to allow airflow
from the soffits into the attic (and then out the roof vents). It is also recommended that efforts are made to seal
around all penetrations in the attic before adding additional insulation.
- A combination of an Airtight Drywall Aproach for a majority of the dwelling’s wall and ceiling surfaces could
be combined with a Flash and Bat system in the attic around penetrations like plumbing, wires, and ceiling pot
lights to provide a functional air barrier. If
- If additional insulation is added prior to sealing the air leaks, the efficiency of the insulation may be
significantly reduced by the air flow AND the risk of condensation in the attic may actually increase. As the
transfer of heat from the home’s interior diminishes, the attic will get colder, which is a good thing in generall,
but if that air leakage brings with it considerable moisture, then the colder temperatures would lower the
dewpoint and contribute to increased condensation risk on the wood surfaces in the attic which will usually
lead to mould and decay.
- As parts of the home do not contain a vapour barrier, other means should be taken to provide a vapour barrier.
A vapour retarder stops vapour by diffusion (which is a lot less severe vapour flow mechanism, compared to
air convection, but still important). Vapour retarders can be created with certain paint primers (when applied
per coverage requirements – heavy coats). It is recommended that these be applied the next time parts of the
interior will be painted.
- No vermiculite insulation was observed at any of the tested locations within the attic.
- The attic hatches were not sufficiently insulated or sealed against air movement.
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不知道如何处理basement,现在是水泥墙,要达到r23需要好几层的保温板,好像不太可行,太厚了。你用spray foam的话墙体有木格栅吗?
