Approaching Zero Energy in Concord, MA

An American classic found in almost every town in the country. The plaster was in great shape and the layout was excellent, so other than adding a few windows and updating the kitchen, we didn’t want to disrupt the interior too much. We almost doubled the living space of this house without adding an inch to the footprint. And the utility bills were cut by 60%.

SPECS:

Conditioned space: 2,000 before, 3,600 after
Bedrooms: 4 before, 4 after
Bathrooms 1 1/2 before, 3 1/2 after
Cost of renovation: $100 per sq. ft.
Annual utility cost:

• Gas $2,400 before, $858
• Electric $960 before, $471

STEPS TOWARDS ZERO ENERGY:

1. Upgrade the mechanicals:

• Furnace: sealed combustion 92% AFUE gas boiler (Munchkin boiler, www.htproducts.com)
• AC: 13 SEER split system in conditioned space
• Hot water: 85% efficient SuperStor tank attached to boiler.
• Outside air is supplied to the return plenum of the efficient air handler; 5 in. pleated media filter in the return path on each air handler.
• Energy efficient low sone exhaust fans in all bathrooms, fully ducted exhaust fan over kitchen stove

2. Bring the basement and crawlspace inside the house -- New 3 in. slab over 2 in. XPS over 1/2 in. drainage mat over old slab; 3 in. closed cell foam sprayed on perimeter walls (R-21), steel studs and drywall over foam insulation as per code.

3. Super insulate and air-seal the roof (R-60) -- R-39 (6 in.) High Density Spray Foam on underside of roof sheathing, R-20 two layers (staggered seams) of foil faced Polyisocyanurate roof deck insulation (3 1/2 in. total thickness).

4. Replace the windows with double glazed low-E replacement windows.

5. Insulate the walls (R-40) -- Cellulose blown into existing 2x4 walls (R-13), two layers with staggered seams of foil faced polyisocyanurate sheathing (R-26).

6. Buy Energy Star (or better) fixtures and appliances --refrigerator,dishwasher, stacked washer/dryer.

MATERIAL NOTES:

• We used closed cell foam in the roof because the rafters were only 7 in deep. Closed cell foam has higher R-value per inch. This allowed us to have the highest possible R-value on the roof without rebuilding the rafters.
• Foil faced Polyisocyanurate to the exterior of the walls gave us the highest R value per inch for the exterior walls. We didn’t want to disrupt the interior plaster to spray foam into the wall cavities.
• Windows - The tilt-in replacement windows were installed from the exterior rather than from the inside so that we could build out the jamb thickness to accommodate the deeper walls. New windows (Andersen, to match the replacaments) were added to the back yard to provide better views to the pond.

LESSONS LEARNED/WHAT WOULD WE DO DIFFERENTLY?
Better windows would be the next place to reduce energy loads in this house. A triple glazed unit, with heat mirror technology might further reduce the heating load allowing us to get closer to zero.

Energy Upgrade in Sommerville, Massachusetts

This is a energy retrofit of a two family Victorian located in a historic district. While historic districts can be quaint, they can also be difficult places for energy retrofits. The enclosure was difficult to upgrade because we weren’t allowed to remove siding or replace windows. We converted the over/under configuration to side by side units and brought the attic into the conditioned space to boost living space. One side is the current home of Building Science Corporation; the other is a rental unit. The basement was made into a warm dry storage area for our massive book inventory. Energy consumption was cut by 50%.

STEPS TOWARDS ZERO ENERGY:
1. Upgrade the mechanicals:

• Furnace: Replace 60% efficient boiler (200,000 Btu) with a two smaller Hydro-air systems. A sealed combustion condensing gas boiler (80,000 Btu, 90% efficient) with water tank (SuperStor Ultra) and a condensing hot water heater (90,000 Btu, 85% efficient) make domestic hot water and provide space heating.
• AC: Window units replaced with direct expansion units (14 SEER) placed on pads in the yard. Energy efficient low sone exhaust fans in all bathrooms, fully ducted exhaust fan over kitchen stove

2. Bring the basement inside the house.

• Drainage mat over existing concrete floor, 2 in. extruded polystyrene (XPS) insulation, topped with a 3 in. concrete slab.
• Sill timbers were lifted off of the brick walls and separated with a capillary break (roofing membrane). 2 in. closed cell foam sprayed to the inside of the foundation and then separated from the interior space with a thermal barrier as required by the building code. In this case, a 1 5/8 in. metal stud wall provides support for paperless drywall (DensGlass gold, www.gp.com).

3. Super insulate and air-seal the roof (R-50)

• Insulation removed between second floor and attic.
• Top plate connected to attic rafters and closed with building paper.
• To adequately support the load of the slate roof, we had to increase the rafters from 2x8 to 2x12. We filled these deep cavities with less expensive open cell foam (www.Icynene.com) (R-40).
• 2 in. XPS below rafters (R-10) provided extra insulation as well as vapor diffusion resistance.

4. Upgrade Windows. We replaced 1/3 of the windows with tilt-in replacement windows. The balance was done with replacement sashes into the existing frames (see materials notes below).

5. Insulated walls. We were able to remove siding to spray in low density open cell foam in 1/3 of the wall area, the remainder of the walls are still uninsulated (see materials notes below).

6. Energy Star (or better) fixtures and appliances

• Energy Star refrigerators (GE and KitchenAide), dish washers (Bosch), and stacking washer/dryers (GE).
• 60% of the light fixtures used were pin based Compact Fluorescent fixtures. The others were period fixtures and were fitted with screw in CFL bulbs.

SPECS:
Completed: 2003
Bedrooms: 4 before, 4 after
Bathrooms: 2 before, 4-1/2 after
Cost of renovation: $125 per sq. ft.
Conditioned space: 2,150 before, 2750 after plus 1,000 sq. ft. of dry warm basement storage.
Annual utility cost: Gas $3,600 before; $1,474 after;Electric $1,200 before; $830 after

MATERIAL NOTES:
Because the roof was covered in slate and the historic commission wanted it to stay in place, all insulation had to be from the roof deck towards the inside. We used open cell foam because the rafters were 12 in. deep; this coupled with 2 in. of XPS on the underside gave us sufficient overall R-value (R-50).

Because the house is in a historic district, we were severely limited in our insulation strategies. On one side we were allowed to remove siding, install house wrap, blow in open cell foam insulation, and replace the siding. On all other sides, we were not allowed to remove the siding in order to tighten up the wall sheathing. For this reason, we were unable to blow in any type of insulation.

The Historic commission allowed us to replace the window frames in the locations where the siding needed to be replaced. All other windows were fitted with new double glazed low e sash. This didn’t improve performance much because the openings were not perfectly square. New windows are double glazed, low-e (www.marvin.com).

Old solid wood doors were salvaged and weather-stripped; some were replaced with energy efficient doors featuring double glazed, low-e lights (www.thermatrue.com).
WHAT WOULD WE DO DIFFERENTLY?
Historic commisions and committees all over the country have interest in windows, chimneys, roof finishes and siding that often conflict with best practice where long term durability of the structure and its energy efficiency are concerned. We compromised and used all wood simulated divided light replacement sashes from Marvin for 2/3 of the window units. Because the openings were so far out of square, the sashes never fit right, and had to be fussed with more than we had expected. We were also not prepared for the battle regarding the siding replacement, and left it until a future phase. It is our intention to go back and replace the balance of the siding, and when we do that, we will blow cellulose into the remaining 2/3 of the wall cavities, and will add insulation sheathing at that time as well. We will brace ourselves for the dialog with the historic committee.

New Home Case Study Template

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(Click all of the labels below that apply to this project


Intro/overview paragraph:

• What style, size, and green ratings did the house achieve.


• Talk about the design program, client’s wishes, tradeoffs such as super insulation gets smaller boiler and better windows, skipped the granite countertops in favor of more sustainable (and cheaper) choice, Smaller footprint in favor of higher level of interior trim detail etc.


• Talk about site: description (urban, suburban, rural, infill, etc.) including environmental concerns and how they reduced the impact of the house including water runoff/erosion (hardscaping/driveways), landscaping (save old trees, plant native species, etc)


• Overview of energy efficiency measures

Team:
Builder:
Architect/Designer:
Engineer:

Specs:
Location:
Completed:
Bedrooms:
Bathrooms:
Cost ($/sf):
Size:

Construction:
Foundation type and R-value (Basement, crawlspace, pier, or slab on grade, R-10 walls, R-5 floor).
Wall construction and R-value: (masonry block, wood frame, SIP, other)
Windows (specs):

Roof construction and R-value (vented or un-vented?):
Garage: Attached, detached, or no garage.

Energy specs:
Conditioning equipment (explain):
Water heating equipment:
Yearly Energy Use (electric, gas, heating oil combined) [See if you can get this, If we can get a HERS score, that may be good enough.]
Modeled or predicted: (kBTU/sf):
Actual : (kBTU/sf):

Water efficiency measures used in this project
Ex. Home run plumbing layout, dual flush toilets, super low-flow shower heads…

Energy efficiency measures used in this project
Ex. Pin-type cfls, motion detector switches, energy star appliances, solar tubes, daylighting with clerestory windows and a light shelf…

Green materials and/or resource efficiency used in this project
Ex: Bamboo countertops grown and manufactured within 500 miles of house, reclaimed flooring, advanced framing, jobsite recycling including grinding drywall for use as road base under driveway or slab…

Indoor air quality measures used in this project
Ex. HRV or ERV brings fresh air into home, no carpets, low VOC finishes on floors and cabinets, furniture made with solid wood, whole house exhaust system, isolation of garage from living space…

Certification:
EnergyStar score (points earned/available):
NAHB green score with breakdown of points earned/available:
LEED-H score with breakdown of points earned/available:
Other certification with breakdown of points earned/available:

Alternate Energy Utilization
Photovoltaic power (size of system): _________; cost $________
Solar water heating (type and size of system): _________, cost $_________
Wind (type and size of system): ________________, cost $_________
Hydro (type and size of system): ________________, cost $_________

Green Building Product Sources:

Lessons Learned:

This section should contain information about the preconstruction assumptions versus the actual performance of the structure. It should include the following:
Construction estimates versus as-built costs
Energy usage versus projected costs
Success of the design/architecture (How well does the house “work” for the occupants, talk to them if possible and have them talk about comfort)Green certifications (Program levels applied for versus what was attained)