Will new siding lower my energy bill?

Siding itself adds little insulation. Savings come from air sealing, a taped weather barrier, insulated siding or exterior foam added during the project, and insulating empty wall cavities.

Is insulated vinyl siding worth it for energy savings?

It adds about R-2 to R-5.5 and covers the wood studs. In one field study, average heating savings were about 5.5%. It is most useful on older, poorly insulated homes in cold climates.

Why is re-siding a good time to improve energy efficiency?

Because the walls are open. The crew can air seal, repair sheathing, install a taped weather barrier and add exterior insulation before the new siding goes on.

Can I get the walls insulated during re-siding?

Often, yes. If the wall cavities are empty, an insulation contractor can blow in insulation from the outside through the sheathing while the siding is off, or from inside. Ask whether your house is a good candidate.

Does house wrap save energy?

A properly installed, taped house wrap reduces air leakage and keeps insulation dry, which helps. Its main job is to manage water.

Does New Siding Save Energy? What Actually Helps

What siding itself does

Standard vinyl, fiber cement and wood siding add very little insulation. The National Park Service’s guidance on historic buildings notes that vinyl is not a good insulator and that siding alone rarely pays back on energy savings. Siding’s job is to shed water and protect the wall. Energy savings from a re-siding project come from what happens behind the siding while the walls are open.

Air sealing: the biggest opportunity

According to the U.S. Department of Energy’s Building America program, air infiltration accounts for roughly 25 to 40 percent of the heating and cooling loads in a typical American house. The same research points out that about 1.1 million homes are re-sided every year, mainly for maintenance and looks – and that air sealing the walls from the outside during re-siding is a promising, often overlooked efficiency measure. With the old siding off, a crew can seal gaps around windows, doors, rim joists, pipes and wires, and install a continuous air and water barrier.

Where walls typically leak air

The rim joist, where the house framing sits on the foundation
Around window and door frames, behind the trim
Where pipes, wires, dryer vents and hose bibs pass through the wall
At the top of walls, where they meet the attic or a porch roof
At joints between additions and the original house

With the siding off, these spots are easy to reach from the outside with sealant, foam and tape – and very hard to reach once the new siding is on.

House wrap and flashing

A properly installed weather-resistive barrier, taped at seams and openings, reduces air leakage and keeps water out of the wall – wet insulation performs poorly. Older homes often have torn building paper or none at all. Replacing it is part of any good re-siding job; ask how seams and openings will be taped and flashed.

Insulated vinyl siding

Insulated vinyl has rigid foam bonded to the back of each panel, typically adding about R-2 to R-5.5 over the studs. That is modest, but it covers the wood framing, which conducts heat much better than the insulation between the studs. In a field study summarized by the Washington State University Energy Program, average heating energy savings at five homes were about 5.5%. Savings are larger in older, poorly insulated homes in cold climates. See our insulated vinyl guide.

Exterior rigid foam

Re-siding is the most cost-effective time to add a continuous layer of rigid foam insulation over the sheathing, because the walls are already exposed. The Department of Energy’s guidance describes the sequence: remove the old siding, inspect and repair the sheathing, air seal, add house wrap, install the rigid insulation and flashing, then the new siding. Exterior foam thickens the wall, so window and door trim must be extended and flashing details change – this is a job for an experienced crew. In wet climates, a rainscreen gap over the foam helps the siding dry.

What about the insulation inside the wall?

Many older homes have little or no insulation in the stud cavities. With the siding off, some contractors can blow insulation into the wall cavities from the outside through the sheathing, or from inside. Ask whether that is an option for your house and who does it – it is often an insulation contractor rather than the siding crew.

Realistic expectations

Measure during re-siding	Energy effect	Notes
New standard siding only	Very small	Protects the wall; little insulation
Air sealing + taped house wrap	Often the biggest gain	Infiltration is 25–40% of heating and cooling loads in a typical home (DOE)
Insulated vinyl	Modest	About R-2 to R-5.5; ~5.5% heating savings in one field study
Exterior rigid foam	Moderate to large	Depends on thickness; changes trim and flashing
Cavity insulation (if walls are empty)	Large in uninsulated walls	Often done by an insulation contractor

Windows and doors

Old windows and doors are often the leakiest parts of a wall. Replacing them at the same time as the siding lets the installer seal and flash them into the new weather barrier in one continuous detail. Even if you keep your windows, re-flashing and sealing the gap between the window frame and the wall during re-siding is worthwhile. See replacing siding and windows together.

Comfort and moisture

Many homeowners notice comfort before they notice their bill: fewer drafts at outlets and baseboards, warmer walls and less noise from outside. Tighter walls also change how moisture moves, so bathroom and kitchen exhaust fans matter, and the wall assembly has to be able to dry. A contractor familiar with building science will think about vapor and drainage as well as insulation.

Incentives and programs

Air sealing and insulation are the measures used in the two largest national programs for existing homes, the federal Weatherization Assistance Program and Home Performance with ENERGY STAR, according to the Department of Energy. Many utilities and states offer rebates or audits for air sealing and insulation – siding itself usually does not qualify. If you are planning a re-siding project, a home energy audit beforehand can show where your walls leak most and whether exterior insulation is worth it. Ask your utility what is available where you live.

Questions to ask

Will you air seal the walls before installing house wrap, and how?
Which weather barrier will you use, and will seams and openings be taped?
Is insulated vinyl or exterior foam an option on my house, and how would trim change?
Are my wall cavities insulated? If not, can they be insulated during the project?
How will the wall dry if it gets wet?

Older homes and safety

If your home was built before 1978, paint on old siding and trim may contain lead; contractors must follow EPA lead-safe practices when disturbing more than 20 square feet of painted exterior. Homes from the 1920s to 1960s may have asbestos-cement shingles under later siding. Both should be addressed before walls are opened.

Does new siding save energy? What actually helps