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 weather-resistant barrier, preventing rain or other forms of moisture from getting into the wall assembly while allowing

water vapor (99.9839 °C) , - , Boiling point , , - , specific gas constant , 461.5 J/( kg·K) , - , Heat of vaporization , 2.27 MJ/kg , - , Heat capacity , 1.864 kJ/(kg·K) Water vapor, water vapour or aqueous vapor is the gaseous pha ...

to pass to the exterior. 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 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 seco ...

and rot can set in and

fiberglass Fiberglass (American English) or fibreglass (Commonwealth English) is a common type of fiber-reinforced plastic using glass fiber. The fibers may be randomly arranged, flattened into a sheet called a chopped strand mat, or woven into glass cloth ...

cellulose insulation Cellulose insulation is plant fiber used in wall and roof cavities to insulate, draught proof and reduce noise. Building insulation in general is low- thermal-conductivity material used to reduce building heat loss and gain and reduce noise tr ...

will lose its R-value due to 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 Tyvek ...

if it is sealed carefully at seams. Housewrap is a replacement for the older

tar paper Tar paper is a heavy-duty paper used in construction. Tar paper is made by impregnating paper or fiberglass mat with tar, producing a waterproof material useful for roof construction. Tar paper is distinguished from roofing felt, which is impreg ...

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

Major types

* 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 propylene. Polypropylene belongs to the group of polyolefins and ...

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 bo ...

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 early ...

") *

Installation

Housewrap must be both water shedding and have a high

moisture vapor transmission rate Moisture vapor transmission rate (MVTR), also water vapor transmission rate (WVTR), is a measure of the passage of water vapor through a substance. It is a measure of the permeability for vapor barriers. There are many industries where moisture c ...

(MVTR) to be effective. It must also take handling abuse during installation and, as housewrap is often left exposed for some time after construction awaiting exterior siding installation, be resistant to UV. 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. Most newer designs do not "seal" well against nails or staples like asphalt products. Housewrap is installed between the sheathing and the exterior siding, and is utilized behind vinyl, wood clapboards, shingles or shakes, brick, and other building materials. In all cases, the housewrap helps prevent water intrusion when moisture in any form gets past the siding and its trim and caulking.

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