excerpt: designing a der

7/27/2019 Excerpt: Designing a DER

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THE GREENED HOUSE EFFEJEFF WILSON

R E N O V A T I N G Y O U R H O M E

A D E E P E N E R G Y R E T R O F I


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THE GREENED HOUSE EFFECT

A Hole in the Bucket: Sealing the Envelope

The building envelope is just what it sounds like: everything that

goes into keeping the outdoors outand the indoors in. Starting from

the exterior surface of a house, a building envelope consists of siding

and roofing, housewrap or roof underlayment, a sheathing material

(usually plywood or oriented strand board, which is not particle-

board, but an engineered wood panel made by layering strands orflakes of wood in specific directions, which are then bonded with

resins under heat and pressure), the structural members (studs and

rafters, for example), insulation material, and even interior finish

surfaces (such as drywall and paint). Fixing the building envelope

is the most critical part of a DER because it affects everything inside

the envelopeheating and cooling efficiency, humidity levels, in-door air quality, and comfort all depend on a well-designed building


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DESIGNING A DEEP ENERGY RETROFIT

FIGURE 3.10Often, older homes are not insulated. When insulation is added later to walls and ceilings, th

and basement arent usually included and air sealing is rarely addressed. The ideal deep energy retrofit bri

building envelope, thermal envelope, and air seal layers into alignment to act as one continuous protective

Insulation layer

Air sealing layerAttic

Living space

Basement

Attic

Living space

Basement

Attic

Living space

Basement

AN OLDER,

UNINSULATED HOME

THE LIVING AREA

INSULATED

A PROPERLY

RETROFITTED HOME


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can develop if the retrofitting of these spaces is done incorrectly. I

explain this in more detail in chapters 5, 6, and 7.

For now lets just say that air sealing and insulation, which

improve your building and thermal envelope, are the first things

youll want to concentrate on in your DER design. Like I said

before, insulation is like a sweater that your home wears and air

sealing is the windbreaker. And just as a windbreaker alone wontkeep you comfortable in frigid temperatures without an insulating

layer, a sweater alone wont keep you comfortable in a biting wind.

You need both, and these layers are the foundations upon which

your DER rests. Depending on where you live, different levels of

insulation may be recommended, but homes in all heating and

cooling climates can benefit from air sealing. As a matter of fact, ifyour house has oodles of insulation but no air seal, your insulation

is not living up to its potential, so getting a handle on air sealing

h i i l


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PLUMBING STACK VENT

BATHROOM FAN VENT

ELECTRICAL

OUTLET

DRYER VENT

ATTIC

HATCH

RECESSED LIGHTS

RECESSEDLIGHTS

CHASE

KITCHEN

FAN VENT

CRAWL SPACE OUTDOOR

FAUCET


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Exterior strategies typically require little interior demolition,

so occupants can remain in the home during the retrofit process.

The typical approach includes expanding the exterior wall or roof

surface outward with spray foam or rigid foam insulating panels.

While spray foam naturally air seals as it expands and cures during

application, rigid panel materials require careful manual sealing at

the joints with tape, caulk, or foam. Its also possible to perform an

exterior gut retrofit by removing all siding and sheathing before

filling the cavities with spray foam from the exterior. Once the

insulation and air sealing is complete, new exterior finish materials

are installed.

Many people overlook basements and crawl spaces in energy

efficiency improvements, but studies show that bringing the foun-dation into the thermal envelope can potentially save 30 percent

on heating costs. Exterior approaches, which require removing

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new windows and doors installed by properly trained profession-

als. This is especially true in retrofitting applications: air sealing,insulation, and water management techniques that may be straight-

forward when installing windows in new homes can become tricky

when incorporating new windows into an older home. The energy

efficiency and operation of many high-end windows have been

compromised by a second-rate installation. This makes it doubly

important to hire a well-trained, competent installer.

The Working Parts: DER Systems

Once the building envelope strategy has been designed, from the

roof and walls to the basement or crawl space, then you can move

on to the systems. Your HVAC system is likely the biggest energyconsuming system in your home. If there were such people as av-

erage Americans, their biggest single point of energy use would

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an important aspect of a full DER. Following Energy Star recom-

mendations is a great start. Bright yellow Energy Star labels ensurethat youre buying an appliance that is at least 20 to 30 percent

more efficient than others in its class. But you can go further by

comparing those labels and choosing the most efficient appliances

within the Energy Star class. That label will also help you make

a better decision when an appliance fails and has to be replaced

quicklyEnergy Star has done most of the research for you and

made it easily accessible right at the point of purchase.

Automation and Monitoring

Last, consider energy monitoring and automation as part of a well-

rounded DER plan. Energy monitoring can show you where mostof the energy is being used in your home and, therefore, where your

money is going. Once aware of those facts, you might opt to change

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can be automated to turn off when rooms are empty, appliances

automated to operate when electricity rates drop to off-peak pric-ing, and outlets automated to turn off when not in use, avoiding

the vampire loads of electronic devices in standby mode. Even

window shades can be automated to let sunlight in or shade it out,

depending on the season.

Does all of this sound a little bit Star Trek to you? Not these

days. We live in a land of touch screens and smart phonesits

about time our homes caught up. Using tablet technology, many

home automation systems provide easy user interface apps to

control any system in the home. These systems can cost from a few

hundred dollars for an off-the-shelf model to many thousands of

dollars for a custom system. Once these automation controls areinstalled, you can enjoy both energy monitoring and automation

for the most energy efficient operation of your home, so beam me

S ! hil l f h i i i l h d


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What Happened In Vegas


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Dream of Big Energy Savings

Thats the grand overview of a DER. Are you overwhelmed yet?

Dont worry, its natural to feel that way when considering a project

as involved as a full deep energy retrofit of your house. Take your

timedont rush the critical design stage and give yourself the lee-

way to dream big at the outset. Remember that a DER doesnt have

to be done all at once, but can be phased in over time, making the

individual phases more manageable.

By the time youre ready to start designing your deep energy

retrofit, youll have a professional energy audit in your hands, and

your auditors report will be a guide that youll refer to over and

over again during the design process. Depending on your comfortlevel you may want to hire an architect or you may feel confident

creating your design yourself. Either way, it helps to start by sketch-

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homes systems will work better, replacing items as they fail. Our

DER took three years of physical work because we opted to do partsof the project ourselves.

While an entire deep energy retrofit is, by nature, not a do-it-

yourself project, you might have the skills to attack some parts of

your DER yourself. Sherri and I hired a contractor to handle the very

heavy lifting and steep roofing jobsthings that would have taken

me months to accomplish alone. Once the house and new addition

were under roof, she and I did the rest of the project ourselves, in-

cluding the exterior curtain wall retrofit and all of the exterior and

interior finish work. This took time but allowed us to minimize the

expense of our DER while still stimulating our economy by hiring a

local crew. Whether youre a hands-on or hands-off kind of person,researching and planning carefully will save you money and result

in a higher quality finished product.

excerpt: designing a der

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