We have two 500' bore holes being grouted now for a closed loop system. We have a new construction house with NOTHING done inside yet.. We plan on sprayfoam insulation. 1-2" closed on roofline with open on top of it to rafters. Open cell everywhere else. The house has zip system sheathing and it is ALSO wrapped (don't ask) So we expect the blower test to be excellent. The house is ~3700 sq/ft but we are spraying rafters so attic will have to be somewhat heated/cooled. We are being quoted $64K ! for a single system with duct work and desuperheater We also have a quote for $57k for a waterfurnace Series 7 5 ton 4-zones comes with a MERV Air Filtration 2 55 gallon electric water heaters (there is radiant tubes in basement) and a dehumidifier.. Thoughts on pricing? or best way to deal with domestic hot water and support the radiant floor in basement. Also I am not 100% convinced that water furnace has a reliable product. It has the variable speed motors I wanted but I see some horror storied about having to constantly reboot it to get it to work and repair nightmares. Comments?
I am bias. I went from many other manufacturers to Waterfurnace about 4-5 years ago. We are the geo the largest geo installer in New York state last year, with 198 heat pumps installed. They were all WF. We have about 380 WF units installed. While there are minor hick ups, e.g. a sensor failed, a circulator pump failed, a thermostat failed, everything was easy to fix, nothing major, about 12 occurrences in total. Much less than any other manufacturer we dealt with. 7 series was the most reliable and had only 4 issues, all with FP1 sensor failure. Usually fixed in 2 minutes. WF has changed suppliers for the sensor. That is it. While not perfect, so far they have given us the least trouble. I think the technology is second to none. Tough to comment about prices in your area, since you might have different labor costs, taxes, etc. Radiant floor should be supplied by a water-water heat pump, is that included? Best way to deal with domestic hot water is also via W-W heat pump. We use the same heat pump for radiant and domestic hot water.
"1-2" closed on roofline with open on top of it to rafters." How deep are the rafters? Spray foam folks sometimes don't go deep enough to get to code R value. I did open cell in my walls, 2 x 6 construction, the building inspector insisted on an interior vapor barrier, which was cocooning the inside with plastic. If your vapor barrier is the sheathing (meaning on the exterior) you need to have a path to the interior for drying, an interior vapor retarder which will allow drying to the interior, plastic on the inside will trap moisture in the wall. How are you heating the water for the radiant? Desuperheater will not do it. CJ
"interior vapor retarder which will allow drying to the interior" We have zip system on the outside taped as well as wrapped (over it). We also have 2x6 walls and intend on using open cell in the walls (for the roof we are thinking 1-2" of closed with the remaining open..). I think you are pointing out that plastic is not a 1-way vapor barrier. Correct? and you are implying the wall has to dry somehow and the vapor from barrier would be "backwards" allowing air from the wall to dry to the inside instead of the reverse? As for radiant.. we will have a desuperheater off the geo.. into a hot water tank (which may not even be powered) for holding.. that feeds into a tankless system that supplies the rediant and domestic hot water... make sense? or is that dumb too? -Ken
Those bids sound about right. Doing it myself is about half that for just materials. Labor would make up the other half and put you right around 60k. Same ballpark as I've seen in bids and other houses with similar systems. Also I am not sure if it's a good idea to use the desuperheater for the radiant.
Just noticed you are in RI and drilling vertical loops and I am in WA with horizontal loops so take that into consideration. Vertical is very expensive out here so Mabey those numbers are really good I don't know.
"or is that dumb too?" I didn't mean to imply anything was dumb, just trying to share so you don't end up with rotten sheathing. I am just a homeowner that has read a lot about building science over the last few years, of course after I built my house, that is my disclaimer. There is a gentleman on greenbuildingtalk.com named Dana1, very knowledgeable about insulation. "I think you are pointing out that plastic is not a 1-way vapor barrier." Yes, it is a barrier, no vapor in, no vapor out, so if you have the zip sheathing taped and wrapped on the outside you don't want a vapor barrier on the inside you want a vapor retarder. Open cell foam is vapor permeable, so you can have moisture in the wall that can't dry to the outside because of the zip sheathing, so a vapor retarder on the inside will allow drying to the inside. Certainteed Membrane is a smart vapor retarder. Does the zip have rigid foam on it to the exterior? What type of tankless is it? Propane/Gas, Electric? Your radiant and DHW share piping (open system) or is there some kind of heat exchanger keeping them separate?
A desuperheater is not a controllable heat source. It is "what you see is what you get" determined by many factors including ground loop temps, HP runtime, mode of operation heating or cooling, DSH entering water temps and others. In the NorthEast depending on actual usage during shoulder seasons the DSH will provide nothing for hot water. During peak heating you might get one tank of hot water a day. Certainly not enough to support your typical radiant floor.
