Thanks udarrell...do these recommendations also apply when there's 20 people in the house? I've been told that each adult is about 800 BTU's worth of cooling and that a properly designed system will factor that in...as well as kitchen stove/oven allowances, etc...
Are those CFM's residential standard or are they calculated per house with manual D/J?
Thanks!
You only allow for the normal occupants of the house. Not for having guest over.
6000 SF House is pretty big... how much of a retrofit are you looking into? If you are just changing the HVAC units go get a HVAC licensed contractor and have them do Manual J load calculations. A red flag response would be that you don't need a load calculation or they come out with a size from experience or off the top of their heads.
Now, if you are re-designing the ductwork and everything else and you really want to have a good system... pay several thousands more and get a mechanical engineer to design everything for you. The "thousands more" part probably doesn't convince you in hiring an engineer but they do have E&O insurance and you are better covered if they mess up.
You can call me Sam
It should be a crime to be a mechanical engineer in San Diego
Summer Design Temperature: 83 F Dry Bulb ~ 69 F Wet Bulb (California Climate Zone 7)
Typically in residential you don't design for maximum occupancy
hvac contractors who size for 100 degree days & 50 people in the
house are just cya to not get call outs on the few days it is actually
100 degrees. properly sized hvac systems, well designed & sealed ductwork
is a much better investment.
fyi..one of the best hvac companies nearby is hvac & plumbing.
different crews for hvac than used for plumbing.
best of luck.
The cure of the part should not be attempted without the cure of the whole. ~Plato
Sam, thanks for the info. The house has no duct work and is finished at this time. It would be a design from scratch. Are you saying good HVAC folks are not equipped to design a retrofit from scratch?
Is it standard for HVAC pros to do "Home Energy Efficiency Audits" done? If not, who does them? Approx cost?
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Last edited by jpsmith1cm; 08-08-2012 at 04:02 PM.
Reason: Non AOP member
This is the Ask Our Pro's forum. In order to post a response here, you must have verified qualifications and have been approved by the AOP Committee. You may ask a question by starting a new thread.
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Additional infractions may result in loss of posting privileges.
I agree that we don't need tax payer incentives to get home owners to make their homes & heating & cooling equipment operating much more efficiently; we need a much better media informed & educated public.
Of course, that was one particular situation that we don't have to repeat.
We contractors through media can inspire & motivate those in the 'Private Sector' where, according to Sen. Tom Coburn (R) of Okla., "there resides 3.6 Trillion dollars in the private sector," | waiting for some of it, to be invested in the multifaceted high-return new Energy Efficiency & Renewable Energy sectors.
We can 'amortize' very low interest rate private sector sourced Micro-loans for Energy Efficiency & Renewable Energy Investments so that the monthly savings more than pays for the energy efficiency & renewable energy sector improvements!
This would solve a multiplicity of costly economic problems while increasing total tax revenues thus reducing deficits, at NO cost to tax payers.
Forget "Cap & Trade," we don't need to raise the cost of fossil fuel energy; my way Reduces Costs & jump-starts the economy & jobs while increasing tax revenues & reducing the huge forth-coming costs of climate change that we are beginning to witness.
Many utility companies are doing free audits or low cost energy audits; even if you didn't do an audit & just evaluated the insulation & plugged every infiltration air-hole U could find, the heat gain heat-loss calcs would be lowered considerable; then seal & insulate the ductwork, if need be, utility bills would be reduced.
I wash my clothes in cold water that I draw & let stand before the next wash, then put detergent in & clothes in to let soak for a number of hours, then they come perfectly clean.
I never use a clothes dryer I hang dry in the house during the winter & on a clothes line in the summer; I live in the country in SW WI.
Think of the energy we could save; my electric bill in an all electric home, during a record breaking June heat wave, thus summer was around $46.00
June 30, 2012; Darrell’s meter; 62610 – May 62140= used 470-KWh * .0985= $46.295 - A Record breaking heat month.
July 31, 2012; 63300 – June 62610 = 690-KWh 67.965 - Another Record breaking heat month - (Two) Half-Ton window units, one upstairs, one on first floor keeping me very cool at all times...
Last edited by jpsmith1cm; 08-08-2012 at 04:02 PM.
Reason: (TWO)... edited post
I have seen plenty of good designs by both HVAC contractors and architects, the key is if they actually do ALL the necessary calculations when designing a system. For example, I would be willing to bet your house has rooms with higher than 8' ceilings and that you will need pretty long duct runs to get from your air handler to the farthest corners of your house. In addition to a Manual J calculation, I would make sure they also perform a Manual D calculation which will help correctly size your ducts.
Also, the other guys are right... residential HVAC aren't sized to include guests. If you like having parties or guest over frequently you may want to look into a two stage AC or have a secondary AC for when you have 20 people over.
You can call me Sam
It should be a crime to be a mechanical engineer in San Diego
Summer Design Temperature: 83 F Dry Bulb ~ 69 F Wet Bulb (California Climate Zone 7)
I'm in favor of loans underwritten or subsidized by a federal program for energy efficiency rather than tax credit, grants and other "hand outs". It seemed to me that you can give out 4 ro 5 loans for every grant... and a lon still makes the person accountable and invested. Low interest rates or long loan terms just make it affordable. Because a long term, low interest rate doesn't have the margin that a private lender is interested in, you may need a program to help subsidize it, similar to some FHA & USDA housing programs. In many rural areas, these go a long way to help improve local, low dollar, aging housing stock. IT makes purchasing a rennovating these properties affordable. We dont need more slapped up stick homes. We have plenty of very well constructed homes out there jsut just have a lot of deferred mainteance.
Hi Folks,
just an update...had my first estimates with one of the companies found through this website. He mentioned 3 separate mini-split systems and 1 conventional central air system.
Although I don't have the estimate yet, he measured all the rooms with a digital device then looked in the attic and the electrical panel.
Should this be sufficient for properly calculating AC needs for the home?
Originally Posted by kingofbytes
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