Adding Insulation to an Older Home:The good, the bad, and the ugly?

Historic Buildings & Green DesignCape-Wide Historic Preservation Workshop

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Sally Zimmerman, Historic New EnglandMarch 25, 2010

There’s always breaking news on the energy front . . . and emerging news on green impacts and preservation

New York Times, March 18, 2010

www.energycircle.com, March 6, 2010

What you need to know before you insulate an older home• What is most often

recommended (and how these recommendations are changing)

• Why these may not be right for the older or historic home

• What you can do to upgrade for energy savings in an older or historic home – appropriately!

A “green” house glossary

Super-insulationInsulating the interior or

exterior to far exceed current building and energy codes

Net zeroA net zero, or zero energy,

structure in general is one that generates more energy than it uses; it can be, but usually is not, disconnected from the power grid. Strictly defined, net zero structures generate no carbon emissions

Deep energy retrofitSuper-insulation, plus the

addition of renewable energy sources or other measures to further reduce the carbon footprint (passive and active solar systems, geothermal, wind power, water use reduction, landscaping)

Passive homeA passive home is so tightly

constructed that it needs no heating or cooling source

HERS Index: Home Energy Rating System

• Set by Residential Energy Services Network (RESNET)

• Scoring system scaled from 0 - 200

• Zero net energy home = 0

• “Reference” new home = 100

• Most older homes = well over 100

• Each 1 point decrease in HERS = 1% reduction in energy consumed

HERS measures: -Building Enclosure -Mechanical Systems -Lighting/Appliances -Renewable Energy

Massachusetts: acting to reduce energy use ahead of federal changes

• First major step towards Zero Net Energy Buildings: amend the State Building Code

• Massachusetts adopted the International Energy Conservation Code (IECC) 2009 as its new state building code, effective January 1, 2010

• Increases energy efficiency requirements by 10% over the current base code

• ZNEB establishes regulatory and financial incentives for deep-energy retrofits

• Directs utilities to pilot 250 deep-energy retrofits in existing homes

Stretch code: local option allows more stringent energy standard that “stretches” the base code requirements• Residential alterations

& renovations can meet stretch code by– Prescriptive path– Performance path

• Prescriptive meets: Energy Star for Homes requirement (HERS 80)

• Performance meets: HERS of 80(houses over 2000 sf)

• HERS of 85(houses less than 2000 sf)

HERS case study for stretch code: Cambridge MA triple-decker, 2009

• Existing = vinyl replacement windows , R-10 ceiling insulation; 11 ACH @ 50 Pascals pressure; no mechanical ventilation

• Initial HERS rating = 143

• Retrofitted with R-13 wall insulation, R-30 ceiling insulation, air sealed to 5 ACH @ 50 Pascals, bath fans added

• Improvement cost = $14,847• Improved HERS = 85

• With 3 new gas boilers @ 86% AFUE

• Upgraded cost = $29,395• Upgraded HERS = 80

http://www.cambridgema.gov/~CDD/et/stretchcode/index.html

What is recommended generally (in the rest of the US)

Oak Ridge National Laboratory:“Insulation Recommendations for Existing Wood-Framed Houses”

Most energy interventions assume your house looks like this . . .

but what if your house looks like this?

Traditional active and passive interventions support energy efficiency in an old house

Traditional practices and design provide the starting point for energy savings

Passive and active energy measures are:- Economical- Reversible- Work with the historic structure and materials

George Nash, Renovating Old Houses

Preservation concerns in insulating older and historic houses . . .

1. We don’t know how these materials and techniques will respond over time (we need more materials science research)

2. It’s complex: contractors are unlikely to know how to properly install them (we need standards for training weatherization contractors on old houses)

3. It’s expensive to do it right (so how many people will be able to afford to retrofit “right”?)

Boston Globe, January 18, 2009“Arlington house may blaze new trail in energy conservation”

Super-insulation/deep energy retrofits of old houses require careful planning and affect historic materials and finishes

Save energy costs and reduce consumption in an older home without losing historic material and character KISSS: Keep it simple, start small•Air Seal-Energy audits using a blower door test show areas of air leakage-Caulk inside and out to close gaps and stop air movement-Weatherstrip windows and doors

•Insulate Attics-Seal areas of air infiltration-Add loose fill or batt insulation

•Seal and Insulate Ducts

•Insulate Hot Water Heaters and Pipes

. . . and REPAIR your wood windows!

Air Infiltration: Blower door test diagnoses sources

Infrared camera monitors locations of heat loss

Comprehensively seal sourcesof air infiltration by caulking gaps

Exterior: Use modified silicone polymer or backer rod and expanding polyurethane foam (foam must be painted to resist weather)

Interior: Use water-based latex

Insulate attics with fiberglass or other batting, or loose-fill insulation; air seal gaps before installing insulation

George Nash, Renovating Old Houses

Seal and insulate ducts; insulate hot water pipes

High efficiency appliances

But what about insulating walls? The big question for old house owners

• Wall insulation is often recommended for energy retrofits in existing houses

• Adding insulation to exterior wall cavities is difficult unless the walls are open

• When walls are insulated, comprehensive measures to air seal, provide proper moisture barriers, and adequately ventilate interior air must also be taken

www.highcountryconservation.org

Wall insulation: not right for all houses• Sprayed in place open or

closed cell foam insulation:– Provides superior

insulation– Comprehensive air

sealing and– Good moisture controlBUT it also:– Requires removal of

interior finishes and plaster and whole house ventilation

– Obscures historic fabric– Is not reversible

Blown-in cellulose: the jury is still out on this . . .Rely on Department of Energy/Oak Ridge National Laboratory web sites for information

DOE and ORNL advise:-adding insulation to an old house is complex and difficult

-older wiring in walls retrofitted with insulation can be a fire hazard

-potential moisture problems must be mitigated through 1) excluding water entry, 2) ventilating interior moisture, 3) stopping air leaks, and 4) providing proper attic ventilation

-More data would help a lot!

The preservationist’s nightmare

Proactive approaches to balancing preservation and energy goals

Older houses (1870-1950)- Use “modern” dimensional lumber, balloon/platform framing- Originally included central heating systems- Often built with stock millwork, trim, architectural elements

Should be able to accept wall insulation without serious loss of integrity

Tailor interventions to age, building type, or significance?

Avoid “energy improvement experiments” on the oldest and most significant properties

“Historic” houses (1680-1850)- Use pre-industrial timber or

Eastern braced framing- Not constructed with central

heating systems

OR

Very significant or rare houses

May not be suitable for wall insulation energy retrofits at

all

Insulation Interventionsfor Older and Historic HousesTo summarize:• Keep it simple, start small

– Air Seal– Insulate Attics– Seal and Insulate Ducts– Insulate Hot Water Pipes• Extensive energy retrofits are costly,

complex, and potentially destructive of historic character and materials

• Be wary of wall insulation• Consider information sources carefully

With care and common sense, every old house can be

GREEN!