Ideally Insulation would have the following characteristics:
Unfortunately there is no product that currently has all these characteristics.
Insulation Problems
Thermal Bridges - Cold is conducted through studs, top plates and sills.
Gaps in Insulation - This can cause convective loops, and as in mineral wool insulation a 4 % gap in the insulation can lead to 30 % loss of R value.
Wind Washing - occurs when wind etc blows through insulation causing loss of R value. This can be corrected by the use of caulking, flashing and weather stripping which all aid in preventing air leaks. Building wraps are also being promoted as preventing wind washing of insulation.
Most Common type of Insulation are: Fiberglass Batts, Blown Cellulose and Blown Fiberglass
Ventilation
The purpose of ventilation is to remove excess moisture from areas such as kitchens, bathrooms and laundry rooms. The moisture is directed to the outside of building and does not allow it to leak into walls and ceilings systems.
We also ventilate non-living areas of the house, such as attics and crawlspaces. The purpose is to remove all heat and moisture that has leaked into these areas before damage can occur.