Most of these are older structures ranging from 1,200 square feet to 2,800 square feet. Each bedroom is often converted to a single or two-person office and the den and/or living room converted to a bullpen office or conference room.
Most buildings were not built with energy efficiency in mind, mainly because most were designed when energy was inexpensive. There is likely little to no insulation and the windows are probably single pane sash. The most common roof is pitched with venting at each end or gable.
The existing HVAC is usually central heating and air conditioning with one unit for each floor. Single supply ducts are typically run to each room from the central unit with one or two common returns per floor. There is one thermostat per floor likely resulting in "hot and cold" rooms. There generally is no mechanical supply of outside air, thus it is supplied by open doors and windows. A whole house fan may have been added at some time for "free" cooling. In most cases the system has never been balanced or formally designed.
Lighting will usually be incandescent surface mounts designed for two or three 60-watt lamps. Each bedroom likely had one fixture and the den or living room, two fixtures.
The electrical system will likely have either a one hundred or two hundred amp main with 120/240 volt single-phase service. The system may not be grounded and if it is the grounding system may be weak. Most cable is not in conduit and may be dry and brittle.
Four, two-lamp incandescent floodlights located at the four corners of the house usually supply exterior lighting. The entrances will usually have one or two surface-mount incandescent fixtures.
The key building energy systems electrical loads are lighting and HVAC. However, after the conversion, office equipment may become a significant load. Some of the key issues to consider in the building energy use during the conversion are:
* Construction materials, amount of glass areas, insulation and orientation to the sun.
* People and activity loading on the HVAC system.
* Required lighting levels.
* Ventilation requirements.
* Balance and control of the HVAC system.
* New voltage and size requirements.
* Power quality requirements.
* NEC and local electrical code requirements.
HVAC
Recommendations/Energy Services Opportunities
The HVAC requirements are likely to change significantly during the conversion from residence to office. This provides a great opportunity to look at system upgrades, including redesign. The basic split system that is probably in place will still be the backbone of the new system, but the following re-designs should be considered:
* Air-to-Air Heat Pumps with the existing furnace used as the backup heat
* Geothermal Heat Pumps
* High Efficiency Air Conditioners.
A new air makeup unit should be installed to supply the required ventilation. The system should be selected to treat the outside air (heated or cooled) so as not to place any overburden on the central system. Heat pipes and/or desiccant wheels should be considered in high humidity areas.
The next step is to do an inspection of the building's insulation. The obvious and easy upgrades will be batt insulation in the floor and ceiling, and either window replacement with double pane windows or the addition of storm windows. Local insulation contractors should be able to provide ideas and cost for insulating the walls if needed.
A heat gain, heat loss calculation needs to be done on the building next. It is necessary to determine the lighting additions - discussed later in this section - and new equipment additions - copiers, PCs, etc. - that will be a part of the conversion. The anticipated people loading, especially in conference rooms, will also need to be determined.
Balancing the supply to each room will be most difficult with the existing ductwork even if it is large enough. Powered supply vents with individual room thermostats may be necessary to get desired conditions in each room. Duct redesign should be the last resort due to cost and difficulty, but the increased internal heat loads might require it.
The final evaluation of the HVAC will be operating cost considerations of the various alternatives. Energy calculations are shown elsewhere.
Water Heating
The existing residential water heater will be sufficient in most applications as the hot water requirements are restricted to hand-washing and some light cooking. If a specialty shop such as a beauty salon is included in the conversion, the additional water heating may be required and sizing issues should be reviewed in the water heating section or the segment section covering that shop.
Lighting
Recommendations/Energy Services Opportunities
The existing lighting levels are probably well below the IES standards for office space. Therefore, two things should be done before you address the lighting system redesign - one - measure the existing lighting levels and compare to IES standards and two - discuss actual versus recommended. The existing levels may be acceptable especially since just an efficiency upgrade will likely increase levels in this case.
The four lighting issues that need to be addressed during the redesign are:
1. Exit Lights
2. Exterior Lighting
3. General Office Lighting
4. Conference Room Lighting
Exit lights will be required at each of the exterior doors of the house. Fire codes may also require signs in hallways and at the top of stairwells. LED exit signs should be used throughout.
Installing additional parking for employees and customers and security lighting needs will likely rise accordingly. This requirement may be met with the utility's lighting services or with an energy customer-owned system. High-pressure sodium or metal halide should be considered - either pole mounted or wall packs. See the security lighting section elsewhere in this CD.
General office lighting should be supplied with surface mounted T-8 fluorescent fixtures. There will be a significant increase in lighting levels with just the conversion from incandescent to the T-8, however, a one for one conversion will still likely fall below the IES standards. If additional light is needed, then fluorescent table and/or floor lamps should be considered before additional ceiling fixtures for cost reasons.
Conference room lighting will have specific needs - primarily dimming capability - that will require a mix of lighting. A combination of T-8 Fluorescent and floodlights should be considered. The floods should be connected to a dimmer switch. A motion sensor should also be considered for the conference room since use will likely be minimal.
Specific details on lighting can be found under the lighting title in the technology section. Useful assistance is also available from most lighting suppliers.
Other Information
Recommendations/Energy Services Opportunities
Power Quality
The most significant change created by the conversion from residence to office may be the importance of power quality. Unfortunately, distribution to most residences is overhead with substantial exposure to weather, traffic and other reliability killers. The residence itself is likely purely grounded - if at all - and may not have enough capacity to handle the new loads associated with the office.
The most useful step in this process will be to first explain the likely reliability issues at the selected location - obtain re-closer and/or breaker operation histories from distribution, and then to determine what reliability is needed by the equipment. The next step will be to determine whether the existing service is sufficient and if not what will be required by code to upgrade it. It may be necessary to seek advice on equipment selection to insure that three-phase equipment is not purchased for a single-phase service.
It will be difficult, if not impossible, to change the distribution system to meet reliability needs. However, there are four areas that can help evaluate cost versus value:
1. Adequate grounding to the system - very important with PCs, copiers and other office equipment
2. Surge protection - consider a meter socket surge protector if your company offers such an option
3. Uninterruptible Power Supplies (UPS) - should be placed on all PCs that have critical information storage
4. Standby generation - may only be necessary for areas that experience periodic extended outages due to storms and other natural disasters