10 Tips for an Energy Efficient Home in the Seattle Area

In what order should you make a Seattle area home energy efficient?

Fix the shell before the equipment. ENERGY STAR advises that before you buy a new heating and cooling system, you address the big air leaks in the house and the duct system (ENERGY STAR, Heat and Cool Efficiently, read October 2026). The table shows the order we suggest (opinion), who usually does each step, and our starting price where we install the work.

Starting prices from our insulation, window and siding pages, October 2026. They include a standard material allowance and are not a quote. "No published price" means we do not list one. Water heating ranks second only to space heating (Seattle City Light, Home Energy Solutions, read October 2026).

Why start with a home energy assessment?

An assessment tells you which of the ten steps your house needs. Puget Sound Energy offers eligible customers an In-Home Energy Assessment at no cost: a PSE Energy Guide walks the house, including the attic and crawlspace, and leaves a report with prioritized recommendations (PSE Home Energy Assessment, read October 2026). The visit takes about 60 minutes, and the Energy Guide does no construction or repairs. A home assessed in the past five years is not eligible, and an online version takes 5 to 7 minutes.

There is a safety reason too. ENERGY STAR warns that sealing a house can make combustion appliances such as water heaters backdraft, and that a home energy professional can test for this before any air sealing (ENERGY STAR, Identify the Problems You Want to Fix, read October 2026).

How much do air sealing and attic insulation save in the Seattle area?

King, Pierce and Snohomish counties sit in climate zone 4C, the marine zone (Washington State Energy Code, Table R301.1, WAC 51-11R-30100, read October 2026). For zone 4C, EPA estimates that sealing air leaks and adding insulation to a typical 1970s or 1980s house saves 13% of the total utility bill and 20% of heating and cooling costs (ENERGY STAR, Methodology for Estimated Energy Savings, read October 2026).

Sealing comes first, while the attic floor is still open. PSE lists the usual leaks as the openings around plumbing pipes, electrical wires and light fixtures in the attic and crawlspace (PSE Weatherization rebates, read October 2026). Then the insulation goes on. On Insulation Installation Services Across the Greater Seattle Area, our Basic attic level is a blown in top up with air sealing, from $5,000+ for an attic up to 1,500 sq ft. Insulating the crawl space and floor starts at $6,000+. A whole house starts at $12,000+.

How deep the attic insulation should be, and what each level includes, is in How Much Does Attic Insulation Cost?

Should you seal and insulate the heating ducts?

Yes, where ducts run through the attic, crawl space or garage. ENERGY STAR says sealing and insulating ducts can improve the efficiency of a heating and cooling system by as much as 20 percent, and it starts with ducts outside the heated space (ENERGY STAR, Heat and Cool Efficiently, read October 2026). Seams get duct mastic or foil tape, then the ducts are wrapped in insulation. PSE runs duct sealing rebates through the same contractor network as its insulation rebates (PSE Weatherization rebates, read October 2026).

When do new windows make a home more energy efficient?

When the old glass is single pane, a sealed unit has fogged, or the sash leaks air. The state energy code sets the bar for every replacement: "Where some or all of an existing fenestration unit is replaced with a new fenestration product, including sash and glazing, the replacement fenestration unit shall meet the applicable requirements for U-factor and SHGC in Table R402.1.3." (Washington State Energy Code R503.1.1.1, WAC 51-11R-50300, 2021 edition, effective 2024). That table sets a maximum U-factor of 0.30 (Table R402.1.3, WAC 51-11R-40213, 2021 edition, effective 2024). The code gives an unlabeled single pane window a default U-factor of 0.95 in a nonmetal or metal clad frame (Table R303.1.3(1), WAC 51-11R-30311, read October 2026), so the gap is large.

Our window replacement starts at $22,000+ for up to 10 vinyl windows with double pane, low E, argon glass, and $38,000+ for 11 to 20. A full install runs about $2,000 to $4,000 per window with flashing, trim and paint. Windows take 4 to 10 weeks to arrive after the order. See Window Replacement Across the Greater Seattle Area. If the old windows must stay, the same code section exempts "Storm windows installed over existing fenestration." (R503.1.1, exception 1).

What should you fix in the walls when the siding comes off?

The weather barrier and any open wall cavity. Siding replacement is when the house wrap and the flashing at each window and door can be replaced, and our Basic siding level includes both, from $35,000+ for a house up to 1,500 sq ft in James Hardie fiber cement. See Siding Contractors Across the Greater Seattle Area.

The energy code does not force new wall insulation when siding is replaced over closed walls. Its alteration rule exempts "Construction where the existing roof, wall or floor cavity is not exposed." Where a cavity is opened, exception 2 sets the minimum: "Existing ceiling, wall or floor cavities exposed during construction provided that these cavities are filled with insulation. 2 x 4 framed walls shall be insulated to a minimum of R-15 and 2 x 6 framed walls shall be insulated to a minimum of R-21." (Washington State Energy Code R503.1.1, exceptions 3 and 2, WAC 51-11R-50300, 2021 edition, effective 2024). Both exceptions hold only "provided the energy use of the building is not increased". Which siding and trim materials hold up to our rain is covered in Construction Materials for Remodeling in the Pacific Northwest Climate.

Does a tighter house need more ventilation?

Often, yes. ENERGY STAR notes that sealing a home may trap pollutants such as radon, carbon monoxide and volatile organic compounds, and that "A tight home may require additional mechanical ventilation" (ENERGY STAR, Identify the Problems You Want to Fix, read October 2026). PSE adds that ventilation keeps moisture from building up in a freshly sealed attic or crawlspace (PSE Weatherization rebates, read October 2026).

Bath and kitchen fans that vent outdoors are the starting point. ENERGY STAR certified ventilation fans use about 48% less energy than standard models (ENERGY STAR, Ventilation Fans, read October 2026).

When should you upgrade the heating system and thermostat?

After the shell, and when the equipment is old. ENERGY STAR suggests having a system more than 10 years old evaluated by an HVAC contractor, and warns that improper installation can reduce efficiency by up to 30 percent (ENERGY STAR, Heat and Cool Efficiently, read October 2026). The same page says a certified smart thermostat can save about $100 a year in homes with high heating bills or homes empty much of the day.

Seattle City Light describes heat pumps as heating and cooling with a fraction of the energy of standard electric heating systems (Seattle City Light, Home Energy Solutions, read October 2026). Install a heat pump after the insulation work, so the contractor sizes it for the smaller heat loss (opinion).

Is a heat pump water heater worth it in a Seattle area home?

For most homes with room for one, yes (opinion). Seattle City Light says heat pump water heaters are 2 to 3 times more energy efficient than conventional water heaters (Seattle City Light, Home Energy Solutions, read October 2026). Placement matters: ENERGY STAR says to install one in an interior space that stays between 40 and 90 F all year, with 1,000 cubic feet of air around it. It runs less efficiently in colder spaces and can cool the room it sits in (ENERGY STAR, Heat Pump Water Heaters, read October 2026). ENERGY STAR also advises planning the replacement ahead, before the old tank fails.

What does the energy code require for new lighting, and which appliance should you upgrade first?

New lighting in a remodel must use high-efficacy sources, unless the work replaces less than 10 percent of the luminaires in a space without raising its lighting power (R503.1.4 exception). The code says "New lighting systems that are part of the alteration shall comply with Section R404.1." and R404.1 says "All permanently installed lighting fixtures, excluding kitchen appliance lighting fixtures, shall contain only high-efficacy lighting sources." (Washington State Energy Code R503.1.4, WAC 51-11R-50300, 2021 edition, effective 2024, and R404.1, WAC 51-11R-40410, read October 2026). Our Lynnwood kitchen was completed in early 2024 for about $50,000. Its scope included new lighting and appliances.

For appliances, look at the dryer. Seattle City Light calls clothes dryers typically the number three energy user in a home, after space heating and water heating, and says heat pump dryers cut that use in half (Seattle City Light, Home Energy Solutions, read October 2026).

How do we plan energy upgrades for a Seattle area home?

We start with the shell: attic, crawl space, windows and walls. At the consultation we look at each one, then send a written, itemized price for the work we install. PSE weatherization rebates are paid only through a PSE Recommended Energy Professional or Trade Ally and come off the contractor's invoice (PSE Weatherization rebates, read October 2026), so ask us about them when we visit. Every insulation job carries a 2-year workmanship warranty, extendable to 5 years.

We work across 132+ cities in the Greater Seattle area, including Home Remodeling Contractors in Bellevue, WA.