How To Look At A House

McGarry and Madsen's home inspection blog for buyers of  

site-built, mobile/manufactured and modular homes

Why is pressure washing double pane windows an expensive mistake?

Saturday, June 30, 2018

Double pane windows provide insulation with an inert gas that the manufacturer seals into the space between the panes. It is usually argon or krypton, both of which are better insulators that air. 

    All insulated windows lose their gas over time as air gradually leaks into the gap between the panes, which brings along moisture. Manufacturers insert a desiccant, such as silica, between the panes to absorb any moisture intrusion, but it eventually becomes saturated and allows condensation to form on the interior surfaces of the glass. Dust in the air collects on the condensation and builds up over time, which gradually clouds the window. This is a normal process for a double or triple pane window as it reaches the end of its lifespan. The cloudiness is a cosmetic issue, but the loss of inert gas reduces the insulating ability of the window and affects the energy efficiency of the home.

    A back-and-forth action that has been dubbed “thermal pumping” contributes to the loss of the gas over time. It is the expansion and contraction, along with flexing in and out, of the glass and surrounding frame and seals with changes in temperature. Sides of a home exposed to direct sun are more prone to the effects of thermal pumping and it can’t be avoided. A window with southern exposure is most likely to have gas loss due to thermal pumping.

    But pressure washing double pane windows creates even more pressure and flexing of the outside pane, with corresponding movement at the seal. It is possible to break the seal sufficiently to lose all the inert gas quickly when blasting a window with high-pressure water. We sometimes visit a home less than 10-years old that the homeowner has pressure-washed and 90% of the windows are clouded over. 

    So don’t do it. Avoid expensive window replacements by washing your windows the old-fashioned way with a soapy solution and garden-hose water pressure. Although pressure washing is one cause of premature clouding of double pane windows, a manufacturing defect or poor installation that squeezes the frame can also cause seal failure. Further investigation may be necessary if you have a large number of windows in your home cloud over at the same time, but no history of pressure washing.

• • • • • • • • • • • • • • • • • • • • • • • • • • • 

  To learn more about doors and windows, see these other blog posts:

What causes sweating (condensation) on the inside of windows in the winter? 

Is every exterior door of a house required to have a landing outside? 

 What are the small slots at the bottom of the outside of my window? 

Why does condensation form on the outside of some windows and not others in the morning? 

Why is the garage door track a white tube? 

What is the raised metal plate on the floor under the garage door?

How many exit doors are required for a house?

 How many exit doors are required for a mobile/manufactured home? 

Are openable windows required to have window screens? Will windows with no screens pass a home inspection? 

Does a home inspector test all the windows and doors in a home? 

How difficult is it to change a window to french doors or a sliding glass door?

How do you determine if a door is left-handed or right-handed?

Why are window security bars dangerous? 

What are the common problems you find inspecting windows?

What is causing a foggy haze on my windows? 

What do those numbers on the manufacturer's stickers in new windows mean?

What does a home inspector check on an electric garage door? 

• What is the tempered label on glass at windows and sliding glass doors called?

• Do I need to have two exterior exit doors in my house? 

• When is safety glass required for windows at stairs and stair landings?

   Visit our DOORS AND WINDOWS page for other related blog posts on this subject, or go to the INDEX for a complete listing of all our articles.

Water Heaters

Water Heater Age

"What Are The

Signs Of..."

Septic Tank Systems

Structure and Rooms

Plumbing Pipes

Termites, Wood Rot

& Pests



When It First

Became Code

"Should I Buy A..."

Park Model Homes


Shingle Roofs




Wind Mitigation

Roof and Attic

"Does A Home


Pool and Spa

"What Is The Difference Between..."




Concrete and

Concrete Block

Metal Roofs


Modular Homes

Rain Gutters

Mold, Lead & Other Contaminants


Older and

Historic Houses

Crawl Spaces

Mobile-Manufactured Homes

Building Permits

Life Expectancy

Clay Soil





Exterior Walls

& Structures


Common Problems

HUD-Code for

Mobile Homes

Garages and Carports

Flat (Low Slope) Roofs

Electrical Panels

Sprinkler Systems

Electrical Receptacle Outlets

4-Point Inspections

Hurricane Resistance

Frequently Asked Questions (FAQ)

Home Inspection

Heating and Air Conditioning

Building Codes

Fireplaces and Chimneys

Inspector Licensing

& Standards

Energy Efficiency

Washers and Dryers



Doors and Windows



Electrical Wiring

Click Below  

for Links

to Collections

of Blog Posts

by Subject

Plumbing Drains

and Traps


Smoke & CO Alarms

Aging in Place

Top 5 results given instantly.

Click on magnifying glass

for all search results.






Air Conditioner & Furnace Age/Size


Electrical Switches





Water Intrusion

Electrical - Old

and Obsolete


Foundation Certifications

Tiny Houses

About McGarry and Madsen



Buying a home in North/Central Florida? Check our price for a  team inspection by two FL-licensed contractors and inspectors. Over 8,500 inspections completed in 20+ years. In a hurry? We will get it done for you.

Moisture Problems

Crawl Spaces