I'm in the process of designing/building a semi-custom house. As far as AC units, any thoughts on the types of AC units (standard vs. Single-speed compressor outside with variable speed air handler on the inside vs. Two-speed compressor outside and variable speed air handler on the inside)?
- Are these the main choices (Gulf Coast/Houston area)?
- Any idea of the % price differences between the types and expected operating cost savings across the different versions?

Any other not so obvious cost-effective features to consider that would help the overall energy efficiency of the home?

I would go 16 SEER with the two speed, if the upgrade charge was reasonable.

People I have seen that go higher than 16 SEER are usually not that happy with the ROI.

Make sure you do Radiant Barrier and try to get R38 on the insulation. Limit the amount of cathedral ceilings in the design and make sure they do more than their average crappy ventilation (especially on the inlet side.) You want constant soffit vents with full baffling, not the little vents spaced unevenly around the perimeter.

Kevin Weiss
http://www.AbsoluteInspections.net

I replaced a 15 year old conventional heat pump unit with a two speed compressor and air handler. I am so far VERY happy with the switch. Much quieter most of the time and with 16 SEER it is clearly cheaper to run.

THe varible speed air handler, with a humidstat is a must. it will dry allot of the air in the house making it feel cooler (sespecially in houston) It does this by running the blower more without the compressor, and ends up saving allot of energy.

I would also consider a Air quality control unit. basically you put a way less obstuctive filter on the intake, and the fine particulate is taken care of the and electrically charged grid. It keeps the CFM high across the A coil allowing for better effciency (if you look at the higher seer rating units they almost always requires this to be used in conjuction to achieve the advertised seer)

1. Have a heat load calculation done on the home prior to purchasing any HVAC equipment. If you have blueprints, doing one is a relatively simple process.

2. Insist on min R 38 insulation in the attic. Don't let them convince you R30 is sufficient, going to R38 isn't that big of a chore and really shouldn't cost you more. Most of the cost is laid in the overhead in getting the truck/men to the jobsite - not the insulation itself.

3. Don't be fooled into icynene foam, it will most likely cause more problems than you'd like.

4. If you can afford a geothermal heat pump system and are planning on staying in the home 10+ yrs - do it. (An entirely different topic).

5. Insist on roof decking with tech-shield. Insist on ridge vents, adequate soffit ventilation. Install an attic tent around your attic ladder if the access is in the home.

6. Insist the HVAC contractor uses mastic around ALL connections (that includes register boxes, plenums, joints in furnace - coil - plenum, duct connections etc.)

7. Visually inspect the HVAC contractors work before agreeing to move forward. Are the duct runs strapped off the floor with minimal bends, kinds, etc.? Is the drain pan large enough so if your coil were to spring a leak (which it most likely will later on) that water will actually go into the pan?

8. If you plan on closing any of your bedroom doors at night, ask that the system be sized/designed with a return grille in each bedroom. (Helps with cooling each room properly - and also reduces stress on the system.)

9. The windows you get will most likely qualify as "energy star". Just make sure they install the windows with the low-e coating pointing the correct way. The last thing you want is for the coating to be pointing into the house... talk about a hot house. (I've seen this done before and the homeowners had already bought new AC systems bc they thought the old ones were too small, etc. etc. etc.)

Are you looking for brand recommendations too?

American Standard & Trane are the EXACT same pieces of equipment... different names & marketing. Similar story for Carrier & Payne,Goodman & Amana, and Ruud/Rheem (Carrier & Payne/Goodman & Amana may have some slight differences, but not much and are essentially the same equipment.)

The only recommendation that I'll make is that the Carrier/Payne variable speed furnace/air handler is pretty fantastic. American Standard doesn't have as many 16 SEER matchups with their VS handlers.

If you live in the great state of Texas, you simply must have a variable speed furnace. There isn't much sense in going to a 90%+ efficient furnace, unless the cost is reasonable.

2 Stage condenser: only if you achieve 16 SEER with the condenser, coil, furnace match up. It is important to verify the con/coil/furn achieve at least 16 through the ARI Certificate. There are some system matchups where the condenser and coil are labeled "13, 14, or even 16 SEER" but don't actually achieve that. The inverse is also the same - some 13 SEER rated condensers achieve 16 SEER with the right coil/furnace matchup.

If they match up, a 2 stage condenser will help immensely. Think of it this way... During the cool(ish), warm, hot, super hot months you have different heat loads on the house. You don't need 100% of the compressing capability every day of the year. Having the capability for the system to "step down" a gear and use less of everything can truly help.

Sorry for the long post, but I believe it makes sense to throw as much info at you as possible when it comes to the HVAC/energy efficiency standpoint as possible to save time/money now.

Thanks for the good feedback.

BKAG---are you in the HVAC business?

Need rec. for Jersey Village area of Houston.

[This message has been edited by 74ZIP (edited 6/21/2011 5:55a).]

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4. If you can afford a geothermal heat pump system and are planning on staying in the home 10+ yrs - do it. (An entirely different topic).

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As someone who is just starting to look at building my "forever" home, this intrigues me. Anyone here have much experience with the ground loop systems currently available? I've done some reading online, but it seems most of that is industry driven and makes promises that are almost too good to be true. Would love to hear from folks, especially in Austin/Central Texas area who have built with these systems.

74ZIP: I used to be, and have a recommendation but he may be out of the city right now. What's your email? Can exchange contact info.

AFA: The company I worked for did some extensive training (I was involved to a point) regarding ground loop systems. They will work very well if a few things are diligently designed and implemented.

1. The depth and number of loops HAS to be sized correctly. You can't design a GHP (ground source heat pump) system without a VERY ACCURATE heat load calculation for the home. You simply MUST have a heat load calculation. It's relatively easy for an air source AC to compensate for lack of or too much capacity. You simply don't have the same luxury with a ground loop system. The loop design has to be precise.

2. The installation of the loops must be done correctly with the correct pipe, the loops must be purged of all air properly, installed to the manifold correctly, purged again, etc. If the loops are installed incorrectly - you're in deep doo-doo. A lot of the companies who have been around do one of two things: 1) Use a drilling contractor who installs/purges the loops themselves or 2) They install/purge the loops themselves. Either can work so long as the installer has sufficient experience.

3. The installation of the rest of the system (the heat pump itself) must be done by an experienced crew. They aren't hard to install, but they are a bit different than a standard AC system, and thus should use a reputable company.

The one system I saw installed was billed as "whisper quiet", but I thought it was rather noisy compared to a "standard AC". If you can design the home as such, you are better for installing the heat pump over a garage area or area that isn't directly above a living area. It may have been that the one we installed had to go through a "break in" period or something (I wasn't with the company long enough to see long-term performance). The noise I heard was the water moving through the system, and it wasn't whisper quiet.

In running the efficiency comparisons for the Houston area (Austin won't be too different), most people will find that a standard HVAC system will do just fine for them in terms of efficiency. Most people live in homes for less than 7 yrs.. nowhere near long enough to see the ROI. If this is truly your "forever" home, them by all means look into a system. They are truly efficient in the long run, have a longer product life, and do just as a good a job when it comes to comfort. The largest cost in a GHP system is the drilling/loop, and those are rated to last 50 yrs. The mechanical components in most are rated to last 20-25yrs as opposed to 10-15 with standard AC.

Again: IF THE LOOP IS NOT DESIGNED/INSTALLED PROPERLY - YOU ARE SCREWED

Bk. My email
1974rwa at gmail dot com

Thanks for the great information. I'm seeing some of the same things about needing 10+ years to really see a return.

For all the reading I've done, I have not seen anything about possible noise problems. I'll definitely add that to the list of things to talk about with the builder. It's great to get info from folks who actually have some experience with these things.

As far as the heat gain calculations, that should be easy to do during construction, right? Is there enough "self-help" material online that I can at least ask the system designer to show me his work and be able to tell if he's done a good job?

AFA -

My pleasure, but please don't consider me the end-all for this information. I'm just a simple guy trying to provide what little info I have so others don't get jammed in the long run.

Yes, a heat load can be done during construction. You don't need one until the final frame/room layout has been completed and shortly before the rough-in stage of the HVAC installation.

If you want to make a decision on whether or not to use GHP vs AC, then settle on your floor plan, and do the heat load calc. The loop design for a GHP system is highly dependent on the load for the home, and as such you won't be able to get accurate bids until the load is done. The drilling contractor charges by the foot whether he's just drilling the holes, drilling & installing loops, etc. I am hesitant to offer my services for heat loads here because I don't want to seem like I'm pandering for business, and I don't carry insurance bc I don't do enough of them on a yearly basis. I typically only do them for a former coworker and friends. But I will however be glad to take a look at yours when it's done and offer any critiques I can. If you have blueprints of your house that you can email, I could take a stab and show you what it might look like.

You can probably become pretty dangerous, maybe too dangerous, when it comes to learning about heat loads yourself. There are some basic principles to follow, but without knowing the software, overreaching design standards, etc. it will be hard to "verify" their work. I'll be glad to compile a list of questions or items to check for in a little while.

[This message has been edited by bkag9824 (edited 6/22/2011 7:45a).]

Wow, thanks. This is why I love TexAgs.

Anyway, we're a long way from actually starting construction. We signed the contract on the land just this week. It is our goal to take our time and do it right with the planning and construction.

I am, however, bookmarking this thread so in a year or two when we actually get around to brass tacks, I can pull it back up.

Great info BKAG.

Great info BK.

I agree pretty much entirely.

Curious about why you are against the foam? I don't see many of these but they appear very efficient. Actually inspected a production builder home yesterday (new construction) that is foamed. First production type builder neighborhood I have seen using this. I also found a roof leak with my infrared camera with water down the complete wall to the first floor. Will be interesting to see what extra steps are needed to fix this. Is very hard to find hard info on the foam and all its variables, potential problems and benefits.

Most people live in homes for less than 7 yrs.. nowhere near long enough to see the ROI. If this is truly your "forever" home, them by all means look into a system.

This is the most accurate statement or most important thing said on here. Do the math. I know the gap is getting closer, but most homes I have built and bid, the 16 SEER takes about 7-9 yrs to re-coup the initial investment. And at that point, the system will be old technology that is darn near warn out.

I put 14 SEER in my homes right now, and just try to insulate them better, and place porches over my large windows to helo with the heat. I also do use energy efficient windows, place trees in "Good" locations, etc. Shade is one of your best friends when it comes to cooling your house.

Absolute -

I may state some things that you already know, but for the sake of others who don't, I'll state my views in length.

I'm against them in the majority of homes as the majority of builders have very limited or no experience with how they change the dynamics of the home.

Homes weren't ever intended to be built like mega-sized coolers. A home that has icynene is intended to minimize the amount of natural air exchange & overall insulation properties - something that is critical to indoor air quality, and the operation/maintenance of HVAC systems.

Too many builders just slap up some icynene, charge a PREMIUM for it, and leave the HVAC to a bunch of billy bobs who don't know how to properly design and install a proper fresh air intake system. Then they show the unsuspecting home-buyer a pretty advertising slick that says "Come buy me! I'm super efficient!". When it should read "Come buy me! I'm super efficient, and my HVAC system has been properly engineered for all the aspects of my home that will in the end make the most difference!" (Quite long winded and obviously not a great selling too).

Most of the homes I've seen with icynene wish they had never gone that route bc they notice higher humidity (gained through the fresh air intake required & improperly designed HVAC), higher utility bills (again because of fresh air), etc. It has typically caused many more problems than it's worth to the average homeowner.

Once you encapsulate the attic space with foam, you have to step up to a 90%+ efficient furnace (= high cost and granted if you're using a new construction loan it's pennies over the long haul), and other variables to consider.

It's great in theory, and does a fantastic job, but frankly there aren't enough contractors who really know what they're doing when it comes to that stuff. The fact that you've found a neighborhood spec builder that's using it is a bit unsettling.

*Again, I'm not the super expert. Just trying to explain what I've seen and how it relates to the average homeowner. I will say that in regards to the GHP systems - if a commercial building - schools, gyms, strip centers, etc. can afford to install one they should. Those types of investments typically pay off in the long run, but not for a homeowner who's most likely trying to keep the cost of a new home below $100 - 200 sqft.

I have seen high end homes with the 90%HVAC and seem at least somewhat "designed" for the foam. I also ran into one that was 5 years old that had a traditional 80% furnace open to the attic. That one seemed like it was an after thought for marketing.

The production one yesterday makes me nervous too. They had installed a heat pump rather than gas - good. They also appeared to under-size (by traditional rules of thumb) the AC which I would think is good from the humidity angle. Did not like that they used a single 5 ton split system rather than two smaller units. I was not particularly impressed with the fresh air system - it was just the standard dumb control - but I am not an expert on what is really available in that area.

I am also concerned about repairs if roof decking needs to be replaced. Or replacing roof decking down the road after a couple sets of shingles are dead. The client said they claimed to have 50 year hail resistant shingles - I told him to get it in writing.

I am also concerned about the moisture we found from the leak - how they will remediate the moisture, replace the wet areas, etc.

I agree that there are a lot of unknowns in the design.

cch,

I agree on your roi theory. Most new homes I see with 14 SEER and 2006IECC are pretty darn efficient and the homeowners are really happy. Hard to suggest upgrades too strongly when they start out pretty good. Have no way to compare the 16SEER people - who also seem happy usually - guess it depends on the cost of the upgrade. But have definitely run into homeowners who have paid lots (10k) to upgrade to 18 or 19 SEER only to talk with their neighbors with the same floorplan and no upgrade and find out they really are not saving much. These people are not happy.

"But have definitely run into homeowners who have paid lots (10k) to upgrade to 18 or 19 SEER only to talk with their neighbors with the same floorplan and no upgrade and find out they really are not saving much. These people are not happy."

This is one of the several reasons I couldn't sell AC systems. Being pressured into selling a product that didn't deliver on it's "advertised efficiencies and ROI" just didn't sit well with me.

Too much hocus pocus for my tastes, and way too much competition.

I realize this question is so general that it may be silly to even ask, but:

Do you have an idea of what the price premium for a ground-loop system over a traditional high-efficiency HVAC system is?

Some of the literature online suggests that a ground-loop system can have positive cash flow from the outset when financed in new construction. I guess the thought is that the extra costs raise your monthly mortgage payment by $X, while your monthly utility savings are greater than $X. I'm curious if there is any rational basis to this, or if it's all sales propaganda.

AFA -

That is a very broad question as most of the cost in a GHP system is locked in the drilling/pipe itself. Drilling rates vary by city to city - state to state due to rock type, water column depth, etc. Drilling rates are higher in Austin than Houston due to amount of rock, etc.

I can't remember the specific rates, but you can do some leg work on your own by calling a couple drillers in your area. Most GHP system drillers started out as water well drillers and made the leap.

[This message has been edited by bkag9824 (edited 6/28/2011 8:34a).]

bkag as some interesting points on geothermal and it absolutely correct about the sizing. There are lot of geothermal fields that are getting to hot of return water and are having problems. If the well field isn't sized big enough then over time it will heat up.

If the goal is to save energy and also dollars I think a bigger bang for your buck is to look into PV's or other renewable along with getting a supper efficient envelope. The risk of geothermal is pretty big. If the well field heats up either from improper sizing and/or bad installation, then you have big problems that are expensive to solve.

If you can get the same energy reduction with PV's for about the same cost as the geothermal, i would go that route. Lots less risk. People who claim they know how to properly size well fields are usually the ones who have had problems.

Houston will require a bigger well field because of the way higher cooling load than heating load.