# Presentation: 033266

## 20 Years of Energy Efficient Buildings& Windows

- Presented by Jim Larsen

## A Hole in the Wall?

## Which Came First?

- Energy Codes
- Or
- Efficient Windows?

## 3 Example Cities........

- Minneapolis	(mostly heating)
- Kansas City	(heating and cooling)
- San Antonio	(mostly cooling)

## Winter -16°FSummer 89°F

- Winter -16°FSummer 89°F

- Winter  2°FSummer 94°F

- Winter 24°FSummer 97°F

## Design Heat Loss20 Years Ago

**Notes:**
Windows are 19-26% of peak heating load

## Priority 1Improve the Envelope

- Increase insulation levels in ceilings, walls, and foundation
- Reduce air infiltration

**Notes:**
80% of heat losss

## How to Improve the Windows

- Every glass layer adds _approximately_ 			1 point to the R-value
- Single Pane		U 1.04	(R1)
- Double Glazing	U 0.48	(R2)
- Triple Glazing		U 0.33	(R3)
- Eight Panes		U 0.13	(R8)

**Notes:**
Beyond double, glass is better than frame.  That’s why NFRC exists!

## Double Glazing Options

- Single Pane + Storm Panel	U 0.48
- Clear 2 Pane Insulating Glass	U 0.48
- Clear 2 Pane IG + Argon		U 0.46
- 2 Pane Low-E	 IG			U 0.31
- 2 Pane Low-E  IG + Argon	U 0.25*
- * optimum for 2-pane glazing

**Notes:**
If window performance doubles save approx 10% on heating

## Triple Glazing Options

- Double Pane IG + Storm		U 0.32
- Triple Pane IG			U 0.33
- Tri-Pane + 1 Low-E	/Argon	U 0.19
- Tri-Pane + 2 Low-E/Argon	U 0.13 *
- * (2) 1⁄4” krypton cavities gives same performance as (2) 1⁄2” argon filled spaces

## Winter Comfort in Minneapolis

## Winter ComfortKansas City and Minneapolis

## Winter ComfortSan Antonio, KC, and MPLS

## Design Heat LossThen & Now

## Heating Summary

- Design heat loss has been reduced approximately 25% in the last 20 years
- Window portion of the peak heating loss has been reduced by about the same amount
- Windows constitute about 20% of the peak heating load

## CoolingThe Other Season for Windows

- Most new homes have air conditioning
- Window solar gain is the single largest contributor to cooling loads

## Single Family Homes Soldwith Air-Conditioning

## Design Heat Gain20 Years Ago

## Priority 1Reduce Solar Heat Gain

- External Shading
- Internal Shading
- Low Solar Gain Glass

## SHGC Requirements in the IECC

## Sunlight Has 2 Equal Parts

- Infrared

- Visible Light

## 50% Solar Gain

- Infrared

- 100% Visible Light

## 50% Solar Gain

- 100% Infrared

- Visible Light

## They look different but have the same solar gain

## Clear Glass85% Solar

- 80% Infrared

- 90% Visible Light

## Tinted Glass49% Solar

- 45% Infrared

- 53% Visible Light

## Reflective Glass  16% Solar

- 12% Infrared

- 20% Visible Light

## “Conventional” Glass Technology

- Clear, tinted, and reflective glasses do _not_ improve the U-factor
- The level of illumination varies but the proportion solar heat gain to light remains similar

## What about Low-E Glass?

- Proven performance for winter heating savings and occupant comfort
- Available today with a variety of solar properties

## High Solar Gain Low-E  60% Solar

- 45% Infrared

- 75% Visible Light

## Solar Control Low-E  40% Solar

- 8% Infrared

- 72% Visible Light

## Tinted Solar Control Low-E23% Solar

- 6% Infrared

- 40% Visible Light

## Design Heat GainThen and Now

## Cooling Summary

- In the southern climates, low solar gain windows and envelope improvements have reduced cooling peaks by 30% or more
- In the northern climates, envelope improvements have reduced cooling peaks by nearly 20%
- High solar gain windows can be nearly 2/3 of the cooling peak in a well insulated house

## Design Heat FlowsThen and Now

## The Next Generation ofEfficient Windows

- Better insulating (triple panes?)
- Less solar gain (reduce daylight?)
- Switchable glass 					(winter gains, summer blockage)
- ??

## Efficient
Windows

**Efficient**
**Windows**

**Energy**
**Codes**