HOME ENERGY SOLUTIONS

Weatherization Specification Manual

UNDERFLOOR INSULATION

UN 1.0—Introduction

Home Energy Solutions underfloor weatherization measures include adding insulation, sealing floor penetrations, adding ventilation, installing a ground cover, and adding water pipe insulation.

If standing water is found in the crawlspace, it shall be drained before the floor can be insulated. A sump pump may be needed for some situations. Draining the water is the responsibility of the owner.

All applicable underfloor areas shall be insulated according to these specifications unless physical barriers exist or this requirement is waived by Home Energy Solutions.

A minimum R-30 insulation shall be used for underfloor installations.

Exception: If floor cavity depth does not allow R-30 insulation without compression, fill the cavity.

Insulation shall be installed so that there is no air space between the top of the insulation and the floor.

Before installing insulation in contact with active knob and tube wiring, wiring shall be inspected and approved in writing by a licensed electrician. Insulating floors with active knob and tube wiring shall be at the discretion of the contractor and homeowner and adhere to state and local code.

UN 1.1—Underfloor Preparation Work

Degradable scrap materials, especially wood and cardboard, shall be removed from the crawlspace. The underfloor shall be checked for water leaks and wood decay before work begins. The owner shall be notified and corrective measures taken, if any are needed.

UN 1.2—Ventilation

Crawlspaces shall be ventilated by openings in exterior foundation walls. Such openings shall have a net area of not less than 1 sq. ft. for each 150 square feet of underfloor area. Where moisture due to climate and ground water conditions is not considered excessive, Home Energy Solutions may allow operable louvers and may allow the required net area of vent opening to be reduced to 1/300 or less (minimum 1/1500), provided the underfloor ground surface area is covered with an approved ground cover.

Openings shall be located as close to corners as practical and shall provide cross ventilation. The required area of such openings shall be approximately equally distributed along the length of at least two opposite sides. They shall be covered with corrosion-resistant wire mesh with mesh openings not to exceed 1/4-inch in dimension. Existing vent openings that are covered with wire mesh need not be modified.

Where venting cannot be reasonably added except by breaching a foundation, ventilation requirements shall be waived.

UN 1.3—Ground Covers

Existing ground cover is acceptable if it meets the requirements for new ground cover. If an existing ground cover does not meet Home Energy Solutions specifications, it shall be repaired or a new ground cover shall be installed.

New ground covers shall be a minimum of 6-mil black polyethylene.

All seams shall be lapped at least 12 inches. The cover shall be continuous throughout the crawlspace. There shall be no rips, tears or gaps.

UN 1.4—Sealing Floor Penetrations

All floor penetrations shall be sealed, including plumbing, wiring and duct penetrations. Caulk, foam, or other compatible sealants shall be used.

Bathtub/shower drain accesses shall be sealed. If the air seal is below the tub/shower trap, leave a small hole at the lowest point in the air seal to allow water to drain.

Illustration UN 1.4

INSTALLING UNDERFLOOR INSULATION

UN 2.0—Basic Installation Procedures

Floor insulation shall be in contact with the floor. Floor insulation shall not be compressed except where required for support, where it is necessary to open a path for crawlspace vents and when R-25 batts are installed in 6-inch cavities. New insulation installed in contact with existing insulation shall not have a vapor retarder.

Illustration UN 2.0A

Insulation shall be pulled free from any temporary stapling. Insulation shall be cut to fit without gaps or overlaps. There shall be no gaps at the perimeter of the foundation.

Illustration UN 2.0B

Insulation shall be supported so that it does not block or restrict crawl space ventilation. Insulation may be compressed, if necessary, to meet this requirement.

UN 2.1—Floor Insulation Support Materials

Use one of the following materials to support floor insulation:

Wood lath—Wood lath shall be a minimum of 1/4 x 1 inch.

Twine—Twine shall be non-stretching polypropylene or polyester.

Wire—Wire shall be stainless steel, copper, or an equivalent material of similar corrosion resistance, with a minimum diameter of 0.040 inch (Size 18 AWG). Self-supporting wire hangers are not acceptable.

Fasteners for lath, twine, or wire may be either hot-dipped galvanized nails or corrosion-resistant staples that are at least 18-gauge and long enough to penetrate wood at least 5/8 inch.

Illustration UN 2.1

UN 2.2—Spacing Requirements for Support Systems

Staples shall be driven with a power-actuated stapler to achieve at least 5/8 inch penetration. Handstaple guns and batt hammers are not allowed.

The maximum spacing for support systems is as follows:

Table UN 2.2

Wood lath shall not be used for spans greater than 48 inches. Splicing is not allowed to meet this requirement. Wood of thicker dimensions may be used for wider spans.

Support systems for spans of over 72 inches require prior approval by Home Energy Solutions.

Batts shall be supported no more than 3 inches from the ends. This support shall be parallel to the end of the batt. Small pieces of insulation shall be supported.

Illustration UN 2.2

Joists may be skipped; however, the maximum spacing shall not exceed 12 inches. The maximum span of skipped joists shall not exceed 48 inches.

UN 2.3—Water Pipe Insulation

All hot and cold water pipes not enclosed within the floor insulation shall be insulated to a minimum of R-3. Leaking water pipes shall be repaired before insulating them.

Water pipe insulation shall be secured with twine, corrosion resistant wire, or plastic compression ties every 12 inches. Tape is not allowed to secure water pipe insulation. Do not cover the handles and spigots of safety drain valves with insulation.

Fiberglass insulation shall have a minimum finished thickness of 1inch. When water pipes run next to a beam or joist, the insulation shall be secured to the beam at a minimum of every 12 inches.

Pre-formed insulation shall be properly sized. Corners shall be mitred to fit tightly. The inside diameter of the pre-formed insulation shall match the outside diameter of the water pipes. Pre-formed insulation shall be supported every 24 inches and within 3 inches of the ends. If connections and corners are larger than piping, exposed joints shall be insulated with fiberglass or pre-formed insulation that matches the outside diameter of the connection and corners.

UN 2.4—Inside Access Doors for Underfloors

Access doors between underfloors and heated spaces shall be insulated to R-25 for floor hatches, and R-15 for doors in walls. Inside access doors shall be weather-stripped.

Illustration UN 2.4

UN 2.5—Outside Access Doors for Underfloors

Any outside access shall have a door that is easily opened to permit inspection, and shall be weather and vermin resistant. Vertical accesses may be screened when it is part of the crawl space ventilation system. Horizontal hatch covers shall shed water. Wood in contact with soil or concrete shall be pressure treated.

Existing covers are acceptable, provided that they are in good condition, weather resistant and vermin resistant.

UN 2.6—Miscellaneous Underfloor Specifications

When installing batt insulation with a vapor retarder, the vapor retarder shall face the heated area of the building. Do not install new insulation with a vapor retarder under pre-existing insulation. Walls between heated areas and crawlspaces shall have all penetrations sealed. Uninsulated walls between underfloors and heated spaces shall be insulated to a minimum of R-15.

Exhaust systems for household appliances—dryers, ranges and miscellaneous exhaust fans—shall be vented to the exterior of the structure. Exhaust systems that do not vent to the exterior shall be extended through to the outside and sealed to prevent any exhaust air from entering back into the underfloor area. Exhaust devices with ducts in a crawl space shall meet the same specifications as exhaust devices venting though attics (sections AT 2.5–2.65).

An air barrier or skirting shall protect underfloor insulation that is exposed to the wind, including unskirted crawl spaces and cantilever floors.

Unheated basements with concrete floors and walls do not require ground covers, foundation vents, or water pipe insulation, except for pipes located on exterior walls. Basements with exposed soil shall have a ground cover installed on exposed areas.