Wednesday, April 7, 2010

HVAC and Plumbing

In addition to the electrical and roofing, the past few weeks have seen quite a bit of work done on plumbing and HVAC (Heating, Ventilating, and Air Conditioning). Apart from deciding on what kind of heating and cooling system to use (we are going with geo-thermal), we also had to determine where all the vents are going to go. The HVAC company basically figured out where they wanted to put everything but then wanted to do a walk-through with us to find out where we will be putting furniture (you don't want a couch right on top of a heating vent). The only room that gave us trouble was our office/guest room. Since this space is designed for dual use, we aren't exactly sure where all the furniture will go in this room.
For the plumbing, instead of using copper tubing they are using PEX tubing (PEX stands for cross-linked polyethylene).  PEX tubing is basically a flexible, plastic tubing that is easier to work with and less expensive than copper.  This makes it easy to run separate hot and cold water lines to each source in the house.  All of these lines come out of a manifold in the basement that has a main hot and cold line running into it.  Since each outgoing line has a valve on the manifold, you can turn off the water to any location in the house from a central location.  This type of topology gives you maximum flexibility and is the same as used with airport hubs and distributed audio systems.

The PEX Manifold (Click image for more photos.)

We had been told that there would be a lot of decisions to make when building a house.  The type and style of flooring, exterior materials and colors, roof shingles, doors, plumbing fixtures, toilets, cabinetry, wall materials and colors, finishing trim, door knobs, cabinet hardware, lighting fixtures, etc.  The list really does go on and on and on.  Even things such as where are you going to hang your towels is an issue because the builder wants to put in "blocking" to provide a sturdier mounting than having to mount into drywall.  It's enough to make you crazy.

For a lot of this stuff, we just wanted something relatively simple and functional.  However, you still need to make a decision, and one of the wonderful--and arguably, one of the terrible--things about America is the overwhelming number of choices that exists for anything you might want to purchase.  One item that we needed to pick out relatively early was the bathtub/shower units.  Do you have any idea how many shower options exist nowadays?  Did you know that you can pay many thousands of dollars simply for the shower "trim" (the faucets and handles)?  Even something relatively simple is manufactured by many different companies and offered with many different options.  Should we simply go with the least expensive model?  Should we opt for the best quality - and if so, how do you determine which is the best quality item?  Even with the internet, researching items is a time consuming and often frustrating process.  In the end, you do the best you can and move on.

Tub/Shower Unit (Click image for more photos.)

One of the big decisions we made early on is to install a geothermal heat pump for heating and cooling.  Heat pumps are very efficient methods of heating and cooling because they don't produce heat, they simply move it from one place to another.  The efficiency of a heat pump (in heating mode) is measured using a term called the Coefficient of Performance (COP).  A good heat pump has a COP of around 3.0-4.0.  When in heating mode, heat pumps take energy from a cold place such as outside (making it  colder), and moves it inside where it is used to warm the house.  In cooling mode, they do the opposite--taking energy out of the inside of the house and moving it to the outside.

Unfortunately, the efficiency of heat pumps decrease as the temperature difference between the warm and cold regions increases.  Thus, if the outdoor temperatures are in the 20's, say, and the indoor temperature is 65, heat pumps are not terribly efficient.  As the temperature difference increases, the Coefficient of Performance of a typical air-source heat pump drops down to around 1.0 or even lower.

Enter the geothermal, or ground source, heat pump.  This type of heat pump uses the ground as it's temperature reservoir.  Since the ground temperature remains a relatively constant 55 degrees year round (regardless of the outdoor temperature), a geothermal heat pump remains very efficient year round.  In winter or summer, a geothermal heat pump works between the temperature of the ground, around 55 degrees, and the temperature of the inside of your house at around 65-70 degrees.  Thus, the maximum temperature difference is only about 15 degrees compared to a traditional heat pump, which can be as high as 50 degrees or even more.  The result is that geothermal heat pumps have a Coefficient of Performance that generally stays above 3.5 or so.

Geothermal Unit (Click image for more photos.)

If they're so efficient, why doesn't everyone use a geothermal heat pump?  Basically it comes down to cost.  While geothermal heat pumps are more efficient and therefore will cost less to run in the long run, they come with a higher upfront cost.  A geothermal unit might run somewhere between $15,000-$25,000 while a more traditional heating system might run about half that (of course, you'll need to add in the cost of an air conditioner as well).  The additional cost comes mainly from all the drilling that needs to be done to take advantage of the Earth's relatively constant temperature.  For a closed-loop vertical system, such as we're having installed, they will need to drill multiple holes hundreds of feet into the ground.  You have to be very aware of the long-term benefits to justify spending the extra money for a geothermal unit.  Fortunately, the US government is giving a tax credit of 30% of the cost (including installation) of a geothermal unit right now.  This makes the cost only slightly higher than a more traditional system.

9 comments:

Kevin said...

Just curious - does the heat pump use electricity at all, or do you basically have "free" heat once you pay the up front cost?

If it does use electricity, what % of typical heating/cooling costs do you expect to pay?

David and Virginia Jackson said...

Kevin - Yes, the geothermal uses electricity. So in terms of "green-ness," the system is only as green as the fuel used to generate the electricity. However, because it is so much more efficient, you will use far less fuel in the long run, so that makes it pretty green. The cost issue is tough to analyze directly because of the varying costs of different types of fuel (gas, oil, etc.). However, the general rule of thumb is that there is a 5-10 year payback time on the extra costs for the geothermal unit. This does not include the federal tax credit, which will substantially reduce that time. But say the geo unit costs an extra 7 grand (probably would be less with the tax credit). Then a 10-year payback would mean about sixty dollars per month in savings (would be higher for a 5-year payback, obviously). We're hoping to put up solar panels on the roof so that the electricity we use will be essentially free to run the system.

Anonymous said...

Wow what a house. I am really excited for you. You no doubt are doing the right thing with your "green" and based on your ages there is little doubt you will get your money back.

Love Mom

Anonymous said...

Priscilla sent me the link to your blog, and I enjoyed reading your progress. From the looks of the pictures, you are using the same wall system that we put in our house in Montana in 2001 - white insulating foam sandwiched between fiber board. It works fabulously for energy conservation, and also provides a very quiet indoor environment. We also have an air-to-air heat exchanger as part of the system. Will you have one? Terri Smiley

David and Virginia Jackson said...

Terry - Welcome to the blog. The answer to your air-to-air heat exchanger question is yes. We've been debating whether to use an HRV (Heat Recovery Ventilator) or an ERV (Energy Recovery Ventilator). They both do about the same thing but there are subtle differences and it's not obvious which would be better in this climate. I'm going do a blog posting on this issue because it's an important one for SIPs construction.

Mike Fowler said...

David,

Read about your house in the paper. How exciting!!! I have a "Drainwater Heat Recovery Pipe" installed in our house in Camp Hill and it works great. I have thermometers hooked up on both the inlet and outlet pipes to measure the heat I'm recoverying. I gain about 10 degrees(from inlet to outlet) when the shower is running and about 15-20 degrees when someone is hand rinsing dishes. I've calculated the payback to be 4.72 yrs and this is how I came up with those figures:


On average heats up our water by 10-20 degrees when taking a shower, or washing dishes. Only recovers heat while hot water is draining and hot water is being required from the water heater.
Conservative savings (1 hour running hot water) = 3 gal/min X 60 minutes = 180 gallons 180 gallons X 10 degrees X 8 BTU = 14,400 BTU's per day
14,400 BTU's / 3412 = 4.22 Kwh per day
4.22 Kwh X $ 0.10 = $ 0.43 per day
$ 0.43 X 365 = $156.92 per year

$ 740 (cost of DWHRS) / $156.92 = 4.72 years payback

I also have a Heat Pump Hot Water Heater that helps cool my house in the summer. I was able to vent the exhaust(42 degrees)to my family room. Payback on this is less than 2 years.

Good luck with your house. I hope you continue to inspire the midstate.

Mike

Jess Holmes said...

Reading about this whole process was very interesting! Greener heating and air conditioning was a priority to me as well when we were working on our house. The people at Warminster air conditioning really helped us out. Best of luck with your new home!

Heating Ontario said...

There are several actions or ways to conserve electricity related to heating and cooling in your home that can also have a positive effect on your electricity bills. Using a programmable thermostat is one of the best ways how to save electricity and energy overall.

Air Conditioner Repairs Mississauga

William John said...

Thanks for the informative article.Heating and Cooling Mississauga

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