Rheem Heat Pump Hot Water Heater

May 24, 2011 by Jeff Erkelens

Riverbluff is the third house where we have used the Rheem Heat Pump Hot Water Heater, as we have been really happy with the results.  Rheem air-source heat pump water heaters work much like a refrigerator in reverse. The heat pump extracts the heat from warm air, intensifies the heat with a compressor, delivers the heat to the water, and exhausts the cooler air. Because it uses the warm ambient air temperature to do most of the work, it is a very efficient way to heat water.

Our greatest attraction to this type of hot water heater is the energy savings.  The estimated annual electric cost for this unit is $234.  The operating cost for most 50 gallon electric water heaters is around $500 or so.  The Rheem Heat Pump Hot Water Heater is costing us about $1600 versus $400-500 for a standard electric.  So, it’s a pretty quick payback of about 4 years.

Realistically, energy efficiency features are still not the major selling point of our spec houses, so I don’t think I’m realizing this extra cost. Or, sadly, I think I could just put a normal hot water heater in and the house would still sell for the same price.  (As an aside, Joey has started to do some research into mortgages that take into account energy upgrades that will lead to a higher monthly payment, but will be made up by lower utilities bills.  Unfortunately, I don’t think the mortgage industry has gotten completely onboard with that.)  Anyway, there is a little bit of a silver lining for us.  This hot water heater, along with a few other features we put into our house, get us to a low enough HERS rating to qualify for a $2000 federal tax credit. The tax credit is for contractors who build new homes that are at least 50% more efficient than a 2004 code built house. This tax credit honestly has helped us adopt certain features as the norm, like an ERV system and the water heater.

Why not gas? Part of it is the extra installation cost of running the gas lines and hooking up a gas unit.  We’re building an all electric house, as we have been really happy with the efficiencies of our ducted heat pump systems and have also switched over to an induction cooktop for the kitchen.  So, it’s hard to justify running gas for just one appliance. Plus, by going all electric, it opens up the possibility of the house being completely supplied by renewable resources in the future when P.V.s become more affordable.

I do acknowledge that the gas tankless has certain advantages, namely the lifespan of a tankless is quite a bit longer than a tank heater.  Plus, as far as energy usage, if you’re a purist, a lot of energy is lost traveling down the electric lines from the power plant to the house. So, if you were to factor in line loss, a gas tankless should be more efficient. At this point, for the small residential scale that we are building at, I don’t think solar hot water makes sense simply because it’s such a long payback time versus the heat pump hot water heater because of the much higher installation cost.

One thing to be aware of is that they are noisy, which we learned the hard way.  We put our first one in on the second floor of the Mulberry house thinking it would be most efficient to be as close to the bathrooms as possible.  Because they are a heat pump, there is fairly audible constant hum to it, which is a little obnoxious. By building high enough crawlspaces, we’ve taken care of the sound issue. Plus, we get the added bonus of the hot water dehumidifying the basement by drawing in warm, ambient air and spitting out cool, dry air.

Special thanks to Eleanor for hopping down to the crawl space to model the Rheem unit.  I mean, wouldn’t you rather look at a cute baby than a boring hot water heater?

Project: Riverbluff Circle · Tags: , , , · Leave a comment

Cooling off, keeping it fresh

June 21, 2009 by Jeff Erkelens

We just got our heating and air conditioning system hooked up and running at the end of the week. To be honest, we haven’t needed it as we have been leaving all the windows open at night to cool the house down. When we get there in the morning, we shut all the windows. With the house being so well insulated, it has been staying in the low seventies inside even when it’s over ninety and muggy outside.

For, the HVAC system, I sort of take things for granted and really don’t think the things we are doing are that amazing. Anybody building to earthcraftt or leed standards is already doing all of this. In the little bubble of friends and like minded builders, it already feels like the norm and not a big deal. But, lot of people are not doing these things, so running through some of the things we did:

properly sized the duct work for each space and properly sized the equipment based on the manual j calculation. Lot of HVAC folks still like to rule of thumb of it rather than sizing things appropriately. Our HVAC guy had two seperate programs run the calculation. One came up with a load that needed a 3 ton heat pump, the other 2.5 ton. We intentionally went with the undersized as it is more efficient and if you oversize a system you leave open the chance for cooling off a space too quickly and not taking the humidity out.

We went with a variable speed air handler, meaning the blower motor ramps up slowly rather than blasting all at once. More efficient, quieter.  We made sure to get equipment  that met the Federal Stimulus package qualifications for energy efficiency to receive the $1500 tax credit to the homeowner.

With the house being so tight because of all the spray foam insulation, indoor air quality can really suffer as you can easily end up with stagnant polluted air.  Pretty much, if you are working with foam, whether it be SIPS, spray foam, superior walls, you have got to introduce fresh air.

We went with a ventilation control that introduces fresh air directly into the return plenum of the air handler. It’s got a damper on it that that is electronically controlled to open at proper time intervals. It also has a temperature sensor and a humidistat, so that it does not open up it is incredibly humid outside in the summer, or below freezing in the winter.  Now they also make a control that costs about three thousand more that conditions outside air on its way in, which is awesome, but I can’t find anything quantifiable that you will ever make your money back on that. The folks at Oak Hill National Labortories are doing some pilot homes where they are trying to achieve a zero energy home and they are just going with the same type we are using, so I feel fine about copying them.

Honestly, the big thing I want to push myself in the coming years is to make the move towards geo thermal because of the greatly increased efficiency and durability of the system. While removing the cap on the tax credits is great, the expense is still  prohibitive. I’m hoping as more people move to it, it will bring the cost down in the coming years.

Project: Rockland Avenue · Tags: , , , · Leave a comment