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Architecture/Design Considerations for Utiliy Elements


Whether for a residential or commercial building, what rules should be followed when programming the necessary rooms/area sizes and locations for mechanical, electrical and plumbing in the initial phases of design?  Book recommendations?

Ex. 1,700 SF house:  water heater can be in laundry, air handling unit in 3'x2' closet in foyer/hall, electrical box in garage or on wall in an utility area.  These are what I can observe but I have no general rules to apply in any given circumstance when arranging elements in a floor plan.


Good question.  If you talk to your local electricians and HVAC contractors, there is never enough room to install and service equipment inside the utility room.  I design commercial buildings and I will always calculate 5% of the overall floor area and allow that for the utility room (water meter, electrical panel, furnace/air conditioner, and water heater altogether).  If I can get the owner to post a sign on the door that reads, "this is not a storage room", then I can focus on other things.

For your small residence of only 1,700 SF, I would still like to see everything together in one room and think carefully about the difficulty while trying to replace the entire furnace 20 years from now.  The most practical variable is whether-or-not your water heater and furnace are using electricity or natural gas (or propane).  If so, then I would consider the following example:

Given a small residence of 1,700 S.F. and a large utility closet that measures 10 feet by 10 feet, I would expect a small 40 gallon water heater to be sufficient.  This water heater would require at least 34,000 btu's.  The furnace/heater size for a 1,700 S.F. house located in New Jersey would be 1,700 S.F. x 30 = 51,000 btu's (more or less depending on air tight seals around windows, thickness of insulation, and number of windows).  Therefore, we have a total gas consumption of 34,000 btu's plus 51,000 btu's which equals 85,000 btu's total required on a very cold day in January.

The minimum amount of combustion air required by Federal regulations is 50 cubic feet per 1,000 btu's.  Verify the code requirements with your local jurisdiction to be certain.  Without sufficient combustion air, the occupant may experience headaches or sickness, or death after breathing carbon monoxide for hours.  Many people feel sick during the cold winter months and believe that these are symptoms of the flu virus.  I would suggest that these folks take two aspirin and then take two minutes to think about how much fresh air is being supplied to their gas-fired appliances.

Next, let's assume that the building contractor for this new house neglected to install the louvered door specified for the utility closet but instead installed a cheap door that allows for very little air leakage.  Remember that we have two pieces of equipment in a 10' x 10' room that are both starving for combustion air.  The cubic feet of air within this room is 10' x 10' x 8' ceiling = 800 cubic feet.  We then determine how many btu's are acceptable for a room this size by dividing 800 cu.ft. / 50 cu.ft. = 16,000 btu's.  But remember we are using 85,000 btu's.  85,000 btu's minus 16,000 btu's equals a difference of 69,000 btu's that need additional fresh air from a fresh air duct or some other source.

To provide fresh air through an outdoor supply duct for 69,000 btu's we need one square inch of duct area for every 4,000 btu's.  In other words, 69,000 btu's divided by 4,000 equals a required clear area of 17.25 square inches.  While a 5 inch diameter fresh air pipe into the furnace room would have sufficient area, we also want to provide a nice thick louver on the exterior of the house with a bug screen to prevent rain, birds, and other crazy things from getting inside the house.  A good louver will then restrict the air flow to only 33% of the covered area.  While a larger louver measuring 9 inches in diameter will cover a hole that is 63.6 square inches in area, it will provide only (63.6 / 3) = 21.2 square inches of air flow which is a little more than the 17.25 square inches required for this example.

In conclusion, you should put your electrical panel fairly close to the electrical meter and remember to provide a minimum clear space of 36 inches by 36 inches in front of the panel.  While sizing the room for your water heater and furnace, it is important to determine first if this equipment is gas or electric.  Remember that some folks will install their equipment so tight that they can't change the filter on the furnace after their done.  You are smart if you provide a floor drain next to your water heater and tie to this same floor drain to the condensate line from your furnace/air conditioner.  Aside from any "rule-of-thumb" numbers used to efficiently squeeze your equipment together and maximize useful living area, you should consider asking your favorite mechanical contractor for help with these important (and practical) considerations.  There is the possibility that providing sufficient space around your utilities could save a sleeping child's life while the entire family thought they were simply sick with the flu.

Richard Burton (architect) is not a mechanical engineer.
It is strongly recommended that you employ the services of a mechanical engineer who is licensed within your state before doing anything involving mechanical equipment and/or mechanical design for commercial projects.
For small residential designs, a licensed heating and air conditioning contractor should be consulted.

Good luck and Merry Christmas.  


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Richard Burton AIA


A combined total of 25 years experience with construction, architecture, and building code enforcement. Ask me about residential and commercial design. Ask me about design aesthetics, structural methods, and building something that will withstand severe weather conditions. Ask me my opinion about YOUR design ideas and I will tell you the merits of good design and challenge your thinking about practical issues. Ask me how to best find and work with your local architect and approach general contractors to get the most value for the least amount of headaches. You can ask me about improving your energy efficiency and things that are both green and practical. But don't ask me about solar panels and wind turbines unless you are currently paying your utility company 35 cents per Kilowatt. Otherwise the math does not justify the initial cost and return on investment. Ask me any building code question and how to get a building permit from the most difficult enforcement agencies.


Here in the midwest, we design and build "green" in ways that make sense. My construction methods prioritize weather resistance, ease of maintenance and durability. While a graduate student in San Diego, I taught drafting and history of architecture. After working ten years for other architecture firms, I have started my firm Arrow Architecture in 2008. More than half of my work involves commercial office buildings. But my portfolio of work also includes custom homes, residential additions, home remodels, and second story additions.

President-Elect of American Institute of Architects - Lincoln, NE

B.S. Architecture - (Interior Design) University of Nebraska Lincoln 1997 Master of Architecture - (Urban Design and Professional Practice) NewSchool of Architecture - San Diego 2004 Graduated Summa Cum Laude ICC Certified Building Plans Examiner

Awards and Honors
AIA Henry Adams Medal and Certificate

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