Contents
- Post Construction Web site
- Overview
- Location
- Selected Photos
- Energy
- Construction <===
- Electrical systems and Photo Voltaic roofing (detail)
- Appliances
- Energy Budget
- Bamboo for flooring and in the garden
- Water conservation
- floor plans and elevations
- Tracking actual progress
Energy Efficiency in terms of building
Environmental Design: An introduction for architects and engineers (2nd Edition) by Randall Thomas is a tutorial for engineers and architects on basic design issue. By using good design principles, one can reduce the total energy budget of the building. However, construction techniques also need to be considered. Building an Energy Star Home means using appropriate materials, modern techniques, and having efficient appliances. The DOE page on Energy star has discussions of lighting, computers, appliances, and general home products. In addition, they have software to allow one to compare alternative ways of improving the energy efficiency of one's current home and links to a number of information sources. "Why houses work, or don't" is part of the homeenergy.org website which includes such things as 13 myths about home energy. They also have a quick review of the systems issues of a home, and the need for contractors trained to consider the entire energy system. Suggestions about optimal use of fans, ducts, lighting and ventilation are available. Training about energy considerations is available at a number of sites in Illinois. Energywisehomes is listed by the Illinois state web page as providing independent energy audits and provides information about Home Energy Rating System required for energy mortgages. The Building Green web site offers subscriptions to their publication "environmental building news" which has some interesting articles. It is also possible to subscribe to the buildinggreen list serve which is a low traffic (about 10 messages/day) list serve of folks interested in helping each other by asking and answering questions about energy usage.
"What are ENERGY STAR¨ Labeled Homes? ENERGY STAR labeled homes offer more home, for less money than standard homes. ENERGY STAR labeled homes use reliable and established technologies and building practices to operate 30% more efficiently than homes built to the Model Energy Code. These technologies and practices save the owners of ENERGY STAR labeled homes money on their utility bills, while also providing a home that's more comfortable, more durable, good for the environment, and cheaper to own."
Energy Star building requires energy efficient windows from providers such as Pella or Loewen as well as efficient building techniques such as adequate insulation and tight duct work. The EPA website offers a pdf file on insulation as well as a webified reprint from 1995 discussing insulation. They link to the National Association of Insulation Manufacturers who then cite the DOE recommendations for insulation by area of the county. For Illinois, they recommend R49 for attics, R38 for cathedral ceilings, R18 for walls, R25 for floors.
For windows one wants to be concerned about the U-factor (lower is better), the Solar Heat Gain Coefficient (SHGC - optimal depends upon heating-cooling concerns), the Visible Transmittance (higher is better), and low Air Leakage. Triple glazing seems to reduce U and hurt SHGC. Window efficiency in U units where U=1/R for comparisons with other insulation. Pella does provide U and SHGC tables, but there are hard to find and do not related to specific products. How do their windows compare to others in terms of insulation and Solar Gain? A Canadian company, Loewen, has a number of pages describing the environmental concerns addressed by their windows (Note that they have completely redesigned their web page and have removed all such useful information). Marvin windows claim to be environmentally friendly but have no test data at all. Cutter seems to provide a number of expensive publications on energy issues for builders. The National Fenestration Rating Council (NFRC) offers a page that allows comparisons of windows by a variety of parameters, including U factors, solar heat gain coefficients, etc.
Heating and Cooling
Heating, Ventilation, and Air Conditioning are among the largest sources of energy consumption in the house. Heating and cooling demands are clearly reduced with the use of proper insulation (see above) but there are still major questions in terms of sizing of systems and sources of heating and cooling. The building specs need to be evaluated in terms of the efficiency requirments of boilers, the estimated heat loss of the building, and comparisons of types of systems. Geothermal heating and cooling is reviewed in its own section.Boiler efficiency is discussed on a number of pages, including those of Weil-McClain and other producers. Weil-McClain suggests the advantage of multiple small boilers rather than one large one. The DOE has a page discussing ways of keeping one's boilers operating efficiently. Given the relatively low heating demands of a well insulated house, it is difficult to see the advantage of multiple boilers. Using solar hot water heating with additional heat being added to the floor heating system seems more reasonable.
Insulation, basic concepts
Heat loss per unit time (in winter) or heat gain (in summer) is a function of the outside tempeature, the desired inside temperature, area exposed, and the quality of insulation. The basic equation is that Heat Transfer (in BTUs) = Difference in Temperature *Area/Insulation.Q = (To-Ti) *Area /R
To make it simpler, the heating and cooling industry thinks in terms of Degree Days = 65 F - outside degrees (F). (This is based upon the finding that houses require heat if the average outside temperature < 65¡ and requires cooling if it is above 65. -- Lets consider heating first.) During the entire year, the average Degree days in Chicago is about 6000 (depending upon whether one uses data from the University of Chicago, Midway Airport, or O'Hare). This obviously varies such that January has far more than July.
Taking rough estimates of the amount of wall area in our house (4350 sq ft), the percentage of that is windows (30%), and the amount of roof (2304 if we assume it is all flat, 2880 if we note that it is pitched), it is possible to show the effect of insulation on heat loss. (Added in October, 2002: note that whole wall R values are less than the estimate for clear or center of wall.) From this it is clear that the biggest effect on energy consumption is in improving the quality of the windows. (Our specs for walls are already at R=21, and the roof at R=38. I am not sure about the basement, which I am estimating at R 15. Nor do I know what to do about the basement floor. Assume its basic area of 48*48 sq. ft. and an R value of 20. )
Insulation and predicted energy use
Using these very rough estimates of insulation suggests that with the predicted insulation and the rough square footages of exposed walls and roofs, that the total energy consumption per year should be roughly 590 Therms for heating with roughly 360 for hotwater heating and cooking. (This does not count the basement. Adding the basement is complicated by realizing that the outside temp is moderated by the earth. Presumably one needs to do wall area times 18-20 degrees since the earth will tend to be about 45-47 degrees year round. An upper bound, assuming no earth averaging effect would add another 259 therms to these estimates.) To validate this estimation technique, I compared these estimates to our current house with the assumption that our current window insulation is about 2.5, the walls about 10, and the roof about 20. These values predict our current gas consumption of 1600 therms/year. (These estimate are probably overly optimistic given the distinction between whole wall and clear wall insulation values, and because our windows are U=.24 rather than the U=.16 that I had somehow come to believe.)
These estimates also lead to the basic model that we need to provide heating (or cooling) of 588 BTU/hour per external degree difference. This suggests that for the coldest day on record in Chicago (-24 F), we would need a furnace with capacity of 65-(-24) * 400 = 52,000 BTU. I assume that builders like to be on the safe side and will suggest a significantly bigger boiler. But anything bigger than about 50K BTU will need to be well justified.
Empirical measurements of heating demand suggest overcapacity by a factor of at least 2
The previous paragraphs were based upon estimates of heating given the insulation of the walls and windows and did not take into account air infiltration. We now have two months of empirical data on energy use. These data probably overestimate typical energy usage because they were collected in the middle of construction without final infiltration minimization. For January, 2003, gas consumption was 464 therms and the AEP degree day history page for Chicago reports 1293 degree days. For February, our consumption was 329 therms and 969 degree days. These lead to empirical estimates of 34,000 to 36,000 BTUs/degree day or 1450 BTU/degree hour. Note that this is roughly twice my original estimate. However, this also shows that on the coldest night ever expected (-20), we would need roughly 120,000 BTU/hour, which is 50% of the capacity recommended (and installed) by the heating and cooling engineer. (He has installed two Weil-McClain GV5 boilers rated at 122 MBH.)
Additional concerns with heating installation
It is also concerning that it seems as if the dual boilers installed are to be run in parallel rather than in series. That is, according to the HVAC technician who is doing the installation, both boilers are to cycle on and off together when heat is demanded. This seems in direct violation of the principles discussed by Weil-McClain in terms of energy efficiency of installing undersized boilers in tandem. This needs to be explored. We also need to be sure to install an external thermostatic control to take into account the outside temperature as well as the temperature within the house.
According to Tekmar control, Outdoor reset thermostats are essential for efficient hydronic heating. In addition, "Multiple Boiler Controls improve the system's operation and efficiency by matching the output of the boiler plant to the load of the system. Outdoor reset increases the seasonal fuel efficiency of the system by operating the boilers at the lowest practical temperature. In addition, the control provides equal run time rotation of each boiler to increase the system's service life. Lower overall operating and maintenance costs makes the use of a tekmar multiple boiler control a practical choice ". We need to insist on outside reset controls.
The EnergyStar webpage provides guidelines for choosing a a heating contractor. "A reputable contractor" should be willing to "Size and select your new equipment using a procedure called Manual J. " and should "Show calculations of savings for installing high-efficiency, ENERGY STAR qualified equipment." I am afraid that we have relied too much on our general contractor's good judgment in choosing a well known HVAC contractor. Although clearly well known (and recommended) in the nothern suburbs, our HVAC contractor has been very unresponsive to our requests for detailed information to check his calculations and has been uncooperative in helping develop meaningful plans. Given the completely inadequate advice with respect to the heating system, we need to rethink the cooling system before we go any further. The advice we have been receiving seems to be of the "figure out the maximum load and then sell the customer twice the requirement" school.
Detailed discussions of how to size, install, and operate a radiant heated floor system is available from a technical manual of a Canadian company (Frontier Plumbing and Heating Supply). Other sources include, of course, the DOE.
An additional item to consider in terms of radiant heated floors is that the floor can not be too hot (greater than 85 or 90 degree F) and thus the heat flow from the floor to the room is limited to the temperature difference of the room and the floor and the area of the floor. According to one source, "The amount of energy a radiant floor heat system can deliver increases with the temperature difference between the radiant surface and the heated space. This amount, in B.T.U. per hour per square foot, has been found to be twice this difference.Ê For example, if the minimum desired temperature of the heated space is 70 degrees F and the radiant surface temperature is 85 degrees F, 30 B.T.U./hr/sq.ft. can be delivered. (2 x delta T = 2 x 15 degrees F = 30 B.T.U./hr./sq.ft.)Ê PLEASE NOTE: To assure occupant comfort in residential and commercial applications it is suggested that radiant floor surface temperatures not to exceed 85 degrees F. For other occupancies such as light manufacturing, factory or warehouse buildings, higher heat loads may require higher surface temperatures."
In terms of cooling, 1 ton of cooling = 12,000 BTU. A rough estimate of the heating output of a person is about 100 W (see a delightful discussion of this as part of a physics tutorial). One can probably assume that we need to provide cooling for a worst case of having 20 people for a party in mid day when it is 95 degree F outside. (Poor planning on our part). This means 20 * 400 + 20*100 which is less than 1 ton of cooling. (Note that including the basement in terms of cooling is probably not necessary given that the earth will act as insulation and will actually provide some cooling rather than require cooling.) Note also that this does taking into account the capacity needed to dehumidify the room.
Whole House fans
An additional cooling technique, much more suitable for our location, is the use of a whole house fan. Given that the evening temperatures tend to be less than 75 (lake temperature), it is possible to keep the house sealed up during the day and then ventilate it at night using a whole house fan. Although most sizing estimates seem to suggest a very large fan capacity (producing 10-20 airchanges an hour), smaller sizes seem more appropriate if used in conjuntion with ceiling fans. It seems as if the larger estimates are based upon the assumption that the fan is providing cooling through the breeze it provides, rather than merely changing the hot internal air with cooler, external air. By using efficient ceiling fans in combination with a smaller, and efficient whole house fan, we can use a much smaller whole house fan. Tamarack Technologies offers a vertically mounted 1,000 or 1,600 cfm fan that can fit into 16" joist or stud spaces and has its own gasketed and insulated (R39) doors.Building techniques
But to be environmentally sensitive is more than just energy efficiency. Issues in renewable building material, low waste building techniques need to be considered. One should also be concerned with the building materials and their sources. SmartWood discusses types of wood use. See also Building Green as a source of materials. Building Green offers a manual (for sale) evaluating various green building products. As an example, sustainable flooring may be made from bamboo or cork. Discussions and examples may be found at JadeMountain (and elsewhere). Bamboo floors seem to be harder than Oak and other hardwoods and are a much more renewable source of flooring. A dealer in Seattle offers a very helpful webpage for customers and architects with instructions of how to lay the flooring in general, and in particular, over radiant heating coils. Vertical grain seems more attractive than flat grain.
The Radiant Panel Association provides useful information about the advantages of radiant heating and also provides training programs for builders. In general, radiant floor heating provides a more even heat than forced air or standard hot water radiators.
Fine Homebuilding provides useful summaries of building techniques and ideas. For example, their discussion of the various parameters of window design (U, E, R, etc.) is very helpful. Discussions of electrical and plumbing issues are educational for me, but probably redundant for architects and builders. R values of walls differ very much as a function of the way they are built. An article comparing the whole wall R value versus the clear wall value is most informative.
Electrical considerations
Photovoltaic systems tend to produce 12 to 48 V DC current. Typically this is converted to AC to allow many appliances to function at 110V AC. There are, however, a number of low voltage DC systems that one uses (e.g., LED and high intensity incandescents, some ceiling fans, many computer equipment). We need to explore the advantages of using (and therefore providing wiring for) low voltage systems, both DC and AC. What is unclear is whether it is advantageous to use DC in some applications. What is clear from an energy perspective is that compact florescents are much more efficient than halogen or other types of incandescent lights.Electrical circuits and wiring
We will need to have house wiring allowing for (at least) 1000BaseT ethernet within the house (Cat 5e wiring) and the possibility of multiple phone lines/room. Although wireless is attractive for many reasons, wired circuits deliver more throughput. (A Mac "Airport" provides 11MB throughput while ethernet delivers 100MB. Next generation intra and internet will be at 1000MB speeds.) A central hub in the basement can provide direct ethernet to each room, particularly the upstairs and downstairs studies. An empty conduit from the basement to my study will allow for future modifications.Current phone usage in our house is 2 voice grade, 1 fax, and one DSL. This is, I believe, the equivalent of 5 twisted pair. Although it would be nice to able to replace all of this with fiber optic cable from a local provider, I doubt if this is a reasonable option for several years. We currently have cable service although we rarely use it. I do not believe cable is available on Lakeside in any case. Wiring the house for cable is probably useful, however. We should explore the possibility of fiber service to the house. It is possible that if several neighbors get together we could get a fiber line. I believe one runs down Sheridan.
Typical "smart house" wiring should allow for at least 1 CAT 5e circuit per room, a typical 3 line phone line, and perhaps a cable outlet. Flexibility suggests a wiring closet in the basement that could hold a DSL modem, a multihub router, and perhaps room for a server. These should be surge protected and have UPS power backup. (See a humorous story on Smart Houses). Also see the British publication on Smart Houses. More information on wired houses is available from Custon Electronic Design and Installation Association (CEDIA).
Cable for audio speakers should connect from the library to the living room, and kitchen, with capability of a cross connect to the basement and the second floor. Second floor speaker cables should connect my study with the bedroom.
X10 technology (or the equivalent) allows remote control of lights and appliances from multiple locations using existing household wiring. There are problems with this technology across different circuits.
Security wiring should include door alarms, breaking glass, smoke and motion detectors. Keypads at the front door and second floor will be needed. It is probably worthwhile to consider window alarms as well. Wiring for these should be planned before windows are installed. Security cameras are available as fake light bulbs.
The Lawrence Berkeley National Labs has a powerpoint (and html) presentation prepared for Pulte Builders comparing the energy savings available if using CFLs in residental housing. They are also collecting data on how much new houses leak air. They have requested leakage test data from new home builders. They also have a discussion of the problem of heating and air conditioning ducts as sources of leakage. They suggest that any such duct work should be run within the insulated part of the house. (Also the source of some Duct Tape Humor.) A link from the LBL is to the Building Science Corporation which has recommendations for building techniques depending upon regional climate concerns. For a cold climate (i.e., Evanston), their recommendations focus on moisture control and insulation. See also the Energy and Environmental Building Association for recommendations on building energy efficient homes.
Fire alarms, smoke detectors, and CO detectors should be installed in appropriate locations. What about a sprinkler system?
Other considerations
Minimizing construction waste and recycling as much as possible needs to be considered. The possibility of salvaging materials from the existing building for use on other sites should be attempted.