Housewrap (or house wrap), also known by the

genericized trademark A generic trademark, also known as a genericized trademark or proprietary eponym, is a trademark or brand name that, because of its popularity or significance, has become the generic term for, or synonymous with, a general class of products or ...

homewrap (or home wrap), generally denotes a modern synthetic material used to protect buildings. Housewrap functions as a water-resistant layer, preventing rain or snow from getting into the wall assembly while allowing

water vapor Water vapor, water vapour, or aqueous vapor is the gaseous phase of Properties of water, water. It is one Phase (matter), state of water within the hydrosphere. Water vapor can be produced from the evaporation or boiling of liquid water or from th ...

to pass to the exterior. It is NOT a weather resistant layer, as weather elements include sun, and housewraps can only be exposed for a few months before being damaged, and temperature, and housewraps do not insulate. If moisture from either direction is allowed to build up within stud or cavity walls,

mold A mold () or mould () is one of the structures that certain fungus, fungi can form. The dust-like, colored appearance of molds is due to the formation of Spore#Fungi, spores containing Secondary metabolite#Fungal secondary metabolites, fungal ...

and rot can set in and

fiberglass Fiberglass (American English) or fibreglass (English in the Commonwealth of Nations, Commonwealth English) is a common type of fibre-reinforced plastic, fiber-reinforced plastic using glass fiber. The fibers may be randomly arranged, flattened i ...

or cellulose insulation will lose its R-value because of the heat-conducting moisture. House wrap may also serve as an

air barrier Air barriers control air leakage into and out of the building envelope. Air barrier products may take several forms: *Mechanically-attached membranes, also known as housewraps, usually a polyethylene-fiber or spun-bonded polyolefin, such as Ty ...

if it is sealed carefully at seams and supported to resist wind loads. Housewrap is a replacement for the older

tar paper Tar paper, roofing paper, felt paper, underlayment, or roofing tar paper is a heavy-duty paper used in construction. Tar paper is made by impregnating paper with tar, producing a waterproof material useful for roof construction. Tar paper is ...

or asphalt saturated felt on walls. It is lighter in weight, available in much wider rolls, stronger, and both faster and easier to apply.

Major types

Nonwoven fabric Nonwoven fabric or non-woven fabric is a fabric-like material made from staple fibre (short) and long fibres (continuous long), bonded together by chemical, mechanical, heat or solvent treatment. The term is used in the textile manufacturing in ...

* Micro-perforated, cross-lapped films * Films laminated to spunbond nonwovens (Typar or CertaWrap) * Films laminated or coated to

polypropylene Polypropylene (PP), also known as polypropene, is a thermoplastic polymer used in a wide variety of applications. It is produced via chain-growth polymerization from the monomer Propene, propylene. Polypropylene belongs to the group of polyolefin ...

wovens * Supercalendered, wetlaid

polyethylene Polyethylene or polythene (abbreviated PE; IUPAC name polyethene or poly(methylene)) is the most commonly produced plastic. It is a polymer, primarily used for packaging (plastic bags, plastic films, geomembranes and containers including bott ...

fibril nonwoven ("

Tyvek Tyvek () is a brand of synthetic flashspun high-density polyethylene fibers. The name ''Tyvek'' is a registered trademark of the American multinational chemical company DuPont, which discovered and commercialized Tyvek in the late 1950s and e ...

") *

Installation

Housewrap is installed between the sheathing and the exterior siding, and is used behind vinyl, wood clapboards, shingles or shakes, brick, and other building materials. In all cases, the housewrap helps prevent water intrusion when liquid water gets past the siding and its trim and caulking. As such, housewrap must be both water shedding and have a high moisture vapor transmission rate (MVTR) to be effective. It must also withstand abuse during installation, and because housewrap is often left exposed for some time before being cladded-over, it must hold up to wind and resist UV for 30 to 90 days. Some new designs must be installed carefully or they will slightly rip or tear during installation, possibly allowing for water infiltration at the damaged areas. Being both thin and inelastic, most newer designs do not "self-seal" well against nails or staples like asphalt products.

Properties

* Typical MVTR ~200 grams/100 square-inches/24hours (or greater, i.e.,

is ~400) * Typical 2 ounces/square-yard (varies greatly with manufacturer) * Typical width 9' (108)" on a 3" core

References

{{reflist Moisture protection Building materials