The wife and I are currently in the process of building our first new home and I am doing my own contracting. I have gotten estimates for heating and air and I am a little over whelmed.
A little info. We are building in SW Missouri. Our new house will be approx. 1650 sq.ft. with a 1100 sq.ft. walkout basement. We have no plans on finishing the basement right away, but will propbably finish out in 5-10 years.
I seem to be getting 2 different schools of thought on my situation. I'm not sure who to believe because I think they are all telling me their way is the best. Some of the estimates I have gotten are for one 5 ton unit to handle both the main floor and the basement. The other estimates are for one 3 ton unit for the upstairs and a 1.5 to unit for the basement. Which is truely the better option? I'm leaning towards the single 5 ton unit and here is why. While the basement is unfinshed, I will leave the vents mostly closed so that the single unit just works on the main floor. Once the basement is finished, I will force more heat towards the basement and force more cooling towards the main floor. Am I way off on this? Keep in mind I now very litle about heat and air.
I'm leaning towards a 5 ton Lennox XP16-060 14.7 SEER or a 5 ton Lennox XP15-060, 15-16 SEER. I'm going to try and hit a mid point between cost and efficiency.
I'll give you a bump. You will need to wait for some of these HVAC guys to reply. I am not in the HVAC business. In my situation a 2400 sq ft ranch over a basement, I have just one unit. In the basement there are only 2 rooms and a bathroom that are heated. It has always worked fine, but I'm not that picky on comfort. That being said 2 units will give you more flexibility and more comfort. You can also zone the single unit and it will work fine too. Depends on the level of comfort you desire and your pocketbook. One advantage of 2 units is if one goes out, you still have the other to take up a little slack. David
With the basement finishing being 5 to 10 years out you don't need to even consider it now other than the air handler location. Have the load calculation's done for the upstair's & install that unit now. If & when you do get ready to finish the basement that's when you'll need the smaller unit for it. Having a unit that much oversized for 5 to 10 years will be nothing but headaches & expence. The contractor's should have told you this.
I would put in first floor unit now, and when you are ready to finish out
the basement put second unit in at that time. Be sure to leave space
allocated for the second unit.
Putting in a single 5 ton unit, and closing off some of the vents that will
serve 1100 square feet is not good. That will put a strain on the 5 ton
unit, and waste energy.
5 tons???? No insulation or all windows? Even with walkout basement, it doesn't add that much to the house. 5 tons seems grossly oversized for new construction assuming you are building it well. I can't fathom 3 ton just for the main floor. Is someone using a load calc to determine this or just guessing? If you really need this much cooling, I'd sure suggest better insulation or something else to tighten the house.
Life Cycle Costs
Options: Zoning and separate dehumification
Originally Posted by crwdz7
or other simplier, less $ set-up
2-stage, high H.S.P.F. heat pump
Back-up: electric or NG ?
Life cycle costs ( initial, operating & warranty) need to be considered.
Electric $0.10 / kW ?
NG $1.20 / therm ?
Specific Energy rates are _ _ _ ?
Long term requirements need to be addressed.
Need independent assistance ...
... send plans and specs ( e-mail in profile).
It's Not Rocket Science, But It is SCIENCE
with "Some Art". ___ ___ K EEP I T S IMPLE & S INCERE
Define the Building Envelope and Perform a Detailed Load Calc: It's ALL About Windows and Make-up Air Requirements. Know Your Equipment Capabilities
And have a real load calc done.
Originally Posted by beenthere
WOW this place is awesome. Those were some quick replies. Looks like the consensus is that the better option would be 2 units and only install the main floor unit at this point. I think the basement should remain relatively comfortable at this time. I will call the companies that I have received estimates from and see if I can get a copy of their load calcs.
As for the specific house construction it is pretty standard. Cellulose insulation in 2x4 walls and relatively few windows. There are only 12 windows, the largest being 4'x5', and 5 of them are only 32"x36".
Dan, if you really don't mind, I can get you that information?
Put the duct work somewhere other than the hot attic.
Air seal the house as much as possible.
Shade as many of the windows as possible during the summer months.
Do all of this and 3 tons may be overkill for your house, including the basement.
Click on the HVAC Calc tab at the top of this page, and purchase the rights to use it for 3 months. Enter in the design of your house, play with different variables until you understand where all of your heating and cooling dollars are going. Then, make appropriate changes to the design of your house. Some changes - like air-tight drywall construction are fairly reasonable in price and invisible when the house is done.
With the right design decisions, you can go with a smaller A/C unit and the upfront savings will pay for the rest. Then, you get cheaper energy bills for the life of the house.
First of all, your basement doesn't add much (if any) to your cooling requirements. You'll need some airflow down there just to keep it from getting musty. Heating is a different story.
I live in the St. Louis area. SW MO is pretty similar in terms of climate. My house is a 5yo 1.5 story with a walkout. First floor is 1500sqft, basement is another 1400sqft. About 500 sqft of the first floor is open to upstairs (19' tall). I've got 5 exterior doors (2 are french) and quite a few 3x5 windows.
The original system installed was a 3.5ton A/C for the main level and basement. It was more than enough, as it was still cycling at 100 degrees. I am now finishing the basement, and changed it out to a 4 ton dual stage Heat Pump. I increased the size to handle the additional basement load during the winter, and got a dual stage so that it could be "smaller" than my old system in the summer.
In my opinion, 5 tons seems WAY too big. I also don't see why you'd need a separate system for a basement. My walkout faces West, I kept the basement vents closed, and it was always cooler than the main level. If it was a two-story house, then get two systems - one for the upstairs, the other for the main level and basement.
Oh, and keep the blower and ducts in the basement. Easier to access, and duct leakage isn't an issue.
The biggest impact you can have (since you are acting as contractor), is to ensure that your building envelope is VERY well sealed. Seal in the attic around can lights, bath fan enclosures, wiring and plumbing penetrations, etc. Seal around the windows. Seal around the band joist. Wrap the house. I wouldn't be surprised to find that 3.5 would be too much as well.
If you get too nervous about whether 3.5 tons can handle it, then just step up to a dual-stage 4 ton. Oh, and HPs heat quite cheaply.
Five tons huh? What do you use for heat load calculation?
Owner-builders usually end up with good air tight homes. This put emphisis on fresh air ventilation. You got some good advice from Dan. Use a whole house ventilating dehumidifier(WHVD) for fresh air and summer humidity control. WHVD will provide adequate fresh air to pruge indoor pollutants, renew oxygen, and <50%RH throughout the home/basement. Also you need make-up air for the clothes drier, bath/kitchen exhaust. I suggest the Ultra-Aire 90H for a MO. 1,600 sqft/house. Regards TB
PS thank you Dan.
Bear Rules: Keep our home <50% RH summer, controls mites/mold and very comfortable.
Provide 60-100 cfm of fresh air when occupied to purge indoor pollutants and keep window dry during cold weather. T-stat setup/setback +8 hrs. saves energy
Use +Merv 10 air filter. -Don't forget the "Golden Rule"