- Q.Is it necessary to put
housewrap behind vinyl siding on new
Paul Fisette responds: Many builders and
material suppliers think that using housewrap under
vinyl siding is a waste of money. I disagree.
Housewrap is cheap insurance, for two reasons: It
protects the building shell from the weather and it
helps save energy.
Vinyl siding is a good siding material, but it
is loose fitting and somewhat permeable to weather.
Wind-driven rain can penetrate at overlapping ends,
around windows at J-channels, at corner posts, at
the intersections between siding and rake trim, and
any other places where joints are involved. A smart
installer should expect water to penetrate the
siding at times; the housewrap provides a backup
weather barrier that allows water to run down and
out without penetrating the structure. Proper
flashings should be used at doors, windows, and
other penetrations, and the housewrap should
overlap the tops of these flashings.
The second issue relates to energy performance.
Studies have shown that air leakage is an important
factor in heating and cooling losses; installing
taped housewrap directly over wall sheathing is a
good way to greatly reduce air leakage. If your
budget allows, a layer of taped foam insulation,
instead of housewrap, will not only reduce air
leakage but also improve the conductive resistance
of the wall.