Saturday, March 7, 2009
Wednesday, January 16, 2008
Light switches impact energy use. Automatic-off, for example, clearly conserves energy. Dimmers, on the other hand, often end up wasting energy. Energy standards such as California Title 24, which may have the best of intentions, are prescriptive. They say what has to be done, rather than allowing creativity and measuring results. The consequence is wasted energy.
California Title 24's (6.1.2, 6.5) regulation concerning incandescent lights in living areas: All luminaires shall either be high efficacy or shall be controlled by an occupant sensor or dimmer.
This rules out using old fashioned switches either way, since (a) if occupant sensors are used with old switches, the sensor has to be able to turn off the light. Without lighting automation, this sensor may prevent turning on the light with the switch. Furthermore, the occupancy sensors are often often visible and ugly, which impacts the feel of the house; or (b) if a dimmer is used, then an old fashioned switch can't be used, since they have no dimmer capability.
Unfortunately, if a dimmer is present, it is common practice to put in bulbs ("lamp it") brighter than the light needed on average, and then use the dimmer. The irony of Title 24 forcing the use of dimmers is that dimming incandescent lights will occur most of the time - and this wastes energy:
- For example, it may be desirable to put in 80 watt bulbs rather than 50 watt bulbs, then dim them for typical use. Incandescent lights are less efficient when dimmed. The 80 watt bulb will use 60 watts to put out the same usable light as a non-dimmed 50 watt bulb because a dimmed bulb will be emitting more radiation in the infrared.
Here is some data from a 100 Watt Bulb, using a high-efficiency Control4 dimmer.
0% -- 0 Watts
25% -- 33 Watts
50% -- 62 Watts
75% -- 87 Watts
80% -- 91 Watts
100% -- 100 Watts
For the example above, dimming a 100Watt bulb to the same visible light output as an 80Watt bulb will consume 91Watts - the difference is extra heat from the bulb. It is far better to install incandescent lights only at the level of typical use, and avoid dimmers.
We thought we pretty much had to go with a Lutron lighting control system to meet Title 24 requirements in various parts of the house, particularly bathrooms. To use antique switches we had to build some special electronics that converts switch signals into commands for the Lutron system.
The on and off switch functions will turn on or off Lutron "scenes" on Lutron "virtual keypads".
Touching and releasing the switch metal is interpreted to perform dimming. For example, when ON, a touch-release-touch-hold will start a dimming cycle that increases and decreases the brightness of the light. When OFF, touching the switch will turn on a nightlight for a limited period of time, and automatically turn it back off.
On-off-on behavior can change Lutron scenes as well. We'll see how intuitive it is to use this control mode.
Each antique switch has 4 wires connecting to a switch board. These connect the switch terminals, and also provide a shielded conductor to contact the switch center. The switchboard contains a low power AVR microcontroller, capacitive sensor logic, a dip switch to indicate the board device ID on the daisy chain, an LED to indicate activity, and an RS-485 connection to other daisy-chained SwitchBoards.
Software on the microcontroller triggers a capacitive sensor for variable sensitivity, monitors and debounces inputs, logs changes with timestamps, and responds to information poll requests for its ID.
A string of these SwithBoards connect (via RS-485 to serial) to a low power JStik computer that is house intranet connected. Java software on this computer polls the switchboards, interprets the switch changes into ON, OFF, ON-OFF-ON, DIM UP, DIM DOWN or NIGHT events. These events are cross-referenced in a lookup table (set via intranet web interface), which presents a Lutron command string to the Lutron controller.
In this manner, the antique light switches perform the functions as necessary required by California Title 24 energy efficiency laws, but look and work as we would like them to. This has the added benefit that most of the commonly used switches in the house are siple.
Permanent fixtures are either high efficiency (flourescent or LED), or they are incandescent but waiting for a good low-power replacement product. We intend to use the lowest wattage incandescent bulbs that do the job until we can replace them with low-power units that work. Stay tuned for a later posting about retrofitting an Iris fixture with an LED luminaire :-)
Wednesday, December 26, 2007
Summer ventilation is accomplished by sucking (warm) air from the ceilings of the second story of the house and venting it outside. This is easy because the second story air return ducts are in the ceilings (see heating and cooling system design).
During winter air inside the house is warmer and more humid than outside air. Straight ventilation would introduce uncomfortable cold drafts, and extra demands on the heating system. A heat recovery ventilator from FanTech is used to heat and humidify incoming air using the outgoing air stream. This air exchange is balanced, so that air pressure in the house is roughly the same as air pressure outside the house. Warm humid air is less likely to seek a path out through walls, windows and doors.
Finally, exhaust vents such as the kitchen hood, bathroom fans and fireplace should not have to fight a tightly sealed house. In our house the EarthTube (summer) and/or HRV inlet (winter) can be activated when the exhaust fans turn on, guaranteeing that air drawn into the house is coming in through desirable intakes.
Ventilation is an Art
- Green builders and homeowners are desparate to find residential HVACcontractors. Today's residential heating/air-conditioning contractors are not familiar with ventilation. Our HVAC contractor is a crossover contractor - they do part commercial and part residential. Several people asked me for our HVAC contractor's contact information.
- The larger Fantech ventilation fans are quite noisy but can also move a lot of air, while the smaller Panasonic fans are whisper quiet by comparison. I intend to do a test run with the house ventilation fans to see how they fare.
- Piping inlet air directly to desired rooms is important, because air flow rates for ventilation are a lot lower than those typical of forced air systems. Very important for bedrooms, since so much time is spent there. Check this in your house!
- Heat recovery ventilators are less efficient with lower delta-T. It is important to duct exhaust air though conditioned space as much as possible prior to connection to the Heat Recovery Ventilator.
- The amount of ventilation (air exchange) required for a building is a function of many things. ASHRAE has a minimum value based on square footage. The baseline air exchange rate we had chosen barely met this number.
Saturday, December 22, 2007
This house makes use of CBF Ultra radiant barrier insulation almost everywhere:
- under roof shingles
- under floors
- under stucco in exterior walls
- inside walls, just behind drywall
- inside basement walls, just behind finish
Radiant barrier behind stucco has an added benefit: it introduces an air gap between the building structure (sheathing, studs, beams) and the stucco. This air gap reduces heat conduction between the building structure and the outside, effectively increasing the insulation value of the walls. This little bit of insulation makes a big difference in the overall insulation value of the wall because the studs and structure have much lower thermal resistance than a foam-filled stud cavity.
For example, consider a 6 inch wall of R25, whose structure covers 10% of the wall area, and is about R6. The wall has an effective R value of R = 1/(0.9*25 + 0.1*6) = R19. If the bubble adds R3.8 everywhere, then the wall's effective R value becomes R = 1/(0.9*(1/(25+3.8)) + 0.1*(1/(6+3.8))) = R24. So adding 1/4 inch of bubble increased the real R value of the entire wall by 20%!
Radiant barrier was the first insulation installed in the second floor of the house, prior to new roof shingles, in mid-summer. The difference was immediate and noticeable. The temperature in the second story dropped 15F, and it was cooler upstairs than it was outside - with no other insulation in place!
Icycene blown-in insulation
The bulk of the insulation is blown-in Icynene. Blown-in insulation does a great job filling areas between wires and pipes, and has no problems filling odd cavities where standard batts of insulation would need to be crammed in (poor insulation) or leave voids (no insulation). Spray-in practically eliminates drafts through walls and ceilings, and thereby substantially reduces problems associated with vapor permeating walls with its resulting condensation.
Rigid Foam Insulation
Rigid foam insulation is used where few interferences exisit: under floors above crawl spaces, under tiles floors over slab, and as insulation in basement walls. Under wood floors in the joist spaces, 3" thickness Dow Thermax board with radiant barrier is used. Its radiant barrier reflects heat back up to the radiant floors. Thinner 1" thickness Dow Styrofoam blue board in combination with CBF Ultra radiant barrier is used over slab floors and behind basement walls.
Fiberglass batts are used to fill larger dead spaces that don't have wiring or plumbing in them, such as cavities under roof walls.
Saturday, September 15, 2007
The tour was a tremendous success, attended by over 50 people. It attracted many silicon valley engineers who are interested in more efficient heating, solar energy, and more efficient water usage. A few architects and at least one contractor (other than this project's general contractor) also attended. Alas, I was too busy to put out a guest book for people to sign.
The high points of the tour ...
The Heat Dissipation Loops in the Pit
- The heat dissipation pipes for our cooling system were visible at the bottom, as were the aluminum heat spreaders both over and under the pipes.
Next, this pit will be partially filled in, and then the storm water dissipation and water storage pipes will be installed.
The Second FloorThe first tour group visitors came up to the second floor of the house at 2:30pm on a fairly sunny afternoon.
The abundant use of radiant barrier was plain to see. There was no other insulation installed yet. And yet it was immediately noticable that the temperature inside was actually very pleasant: it was not hot at all.
The radiant barrier fulfills several functions in the slanted roof: it serves as an insulation stop, so that insulation that is blown in will not go thought the wood roof shingles, it serves as a radiant barrier directly under the skip sheathing to which the wood shingle roof is attached, and it serves as an insect barrier, so that wasps or bees don't build a hive in the stud bays (we discovered a few when the walls were opened).
The Wine Cellar
Many wine cellars are designed with expensive refrigeration systems, and can keep wine at 55F so that bottles can mature over the course of 100 years. These refrigeration systems cost a lot of money to buy and operate.
My goal is to build a wine cellar that can hold decent wines at 60F, aging them over a period of 10 to 20 years, so I can enjoy them during my lifetime :-)
This cellar is designed to take advantage of relatively stable (60F) temperature at 12 feet of depth - which is the yearly average temperature of the San Francisco Bay Area. To do this well, the cellar is built deeper into the ground than the rest of the basement.
In spite of the lack of insulation, no door, and it being the end of the summer, the cellar temperature was 62F during the tour. I don't believe there will be any trouble achieving the target temperature of 60F.
There were some good discussions regarding the installed shower heat reclamation plumbing, the two examples of more efficient insulation and heating for the tile floor areas, and the frustrations with thrying to get greywater irrigation approved - even in this water conservation climate.
Visitors got to hear about (and critique) some of the planned experiments in heating and cooling. I welcome this feedback, and endeavour to produce data over time to show how well things actually work.
Tour Site Placards, as an online presentation. Some photos taken by a visitor.
I'd like to thank my wife Patti who took care of tasty refreshments for the visitors. I'd also like to thank my contractor Bernie and his staff for doing a great job presenting a clean and safe site, for last minute help putting up the informative signs and especially to Bernie for being available to answer many questions. Finally thanks to my friend Andy, a mechanical engineer, for answering questions for people who didn't quite catch the first tour but couldn't stay for the second.