Energy-Efficient Window Installation in Sunnyvale, CA
In Climate Zone 4 the number that matters is solar heat gain. We spec the glass to the label, not to a national default.
Two Numbers Decide Whether Glass Works Here
Low-E, argon-filled, ENERGY STAR qualified units chosen for the local climate and installed to spec.
Every NFRC label carries two numbers. U-factor is how fast heat moves through the whole assembly. SHGC, solar heat gain coefficient, is how much of the sun's energy the glass lets through. Lower is better on both.
Sunnyvale's problem is the second number. We get long dry heat and mild winters, so the money is in stopping afternoon sun rather than holding heat in. A cold-climate package shipped nationwide gets the U-factor right and leaves the SHGC too high for a west-facing wall here.
Signs Your Glass Is Costing You Money
A PG&E bill that jumped
Same habits, same house, sharply higher summer usage. Single-pane glass on a sun-facing wall is a common cause.
West rooms unusable after 3pm
The room heats through the glass faster than the air conditioning can pull it back.
HVAC that never catches up
The system runs continuously through the afternoon without reaching the setpoint.
Faded floors and furniture
Unfiltered ultraviolet through untreated glass bleaches wood, fabric, and artwork.
Original single-pane aluminum
An aluminum frame conducts heat straight through the wall. It is the worst assembly in most Sunnyvale tract homes.
A permit triggering Title 24
A remodel or a window permit brings a compliance requirement your glass has to actually meet.
How We Do It
- Step one
Walk the house by orientation
We note which elevations take afternoon sun and which are shaded. That changes the spec wall by wall.
- Step two
Spec per elevation
A lower SHGC package on the west and south, a clearer package on the north where you want the daylight.
- Step three
Install to the label
A good U-factor is thrown away by a bad air seal. Flashing, insulation, and sealing are what make the number real.
- Step four
Hand over the paperwork
NFRC labels and the Title 24 compliance documentation, so the permit closes and you have the numbers on file.
Title 24 Is a Real Number, Not a Slogan
City of Sunnyvale permits require Title 24 compliance documentation for window replacement. That is a number your glass has to hit, and it is one reason a written quote should name the product line and the label values rather than saying energy-efficient windows and leaving it there.
ENERGY STAR qualified
NFRC-labelled units, with the label values written into your quote.
Spec'd for Climate Zone 4
Solar heat gain prioritised, per elevation, rather than one package for the whole house.
Title 24 paperwork handled
We pull the permit and prepare the compliance documentation.
Energy Performance Questions
As a working baseline we spec U-factor at 0.30 or better and SHGC at 0.23 or better, which comfortably clears the current Title 24 prescriptive path for this climate zone. On a heavily shaded north wall a higher SHGC is fine and gives you more daylight.
Replacing single-pane glass on sun-facing walls makes a difference you can feel and usually see on the bill. Replacing sound double-pane windows with newer double-pane does not, and we will tell you that rather than take the job.
It is California's building energy efficiency standard. Replacing windows under a City of Sunnyvale permit triggers it, and the replacement glass has to meet the required performance values. We prepare the documentation as part of the job.
Federal efficiency credits and utility programmes exist and the terms change year to year. We will tell you which ones your product line qualifies for at the time of quote, and give you the NFRC documentation you need to claim. We do not promise a specific dollar amount.
Related Services
See the Label Values Before You Buy
We walk the elevations, spec the glass wall by wall, and put the product line and its NFRC numbers in the written quote. Then you can compare it to anyone else's.
Contact DetailsFree in-home measure
(408) 547-4680 — talk glass packagesMonday to Friday 7:30am to 5:30pm · Saturday 8:00am to 2:00pm