EcoRenovator - View Single Post - Design and Build Spiv's Solar and Geothermal House

DEnd · 07-03-16, 07:35 AM

Spiv,

It sounds to me like you have a fairly low heating load. In that case for choosing equipment I would go for a heat pump over geothermal. I would also forgo hydronic in floor heat, simply because you seem to be in a mild climate. If you are indeed in a mild climate, I encourage you to look closely at the Passivhaus concept. If I remember correctly you already have plans drawn up? If so I doubt you can really go whole hog on a passivhaus but it's concepts are hugely helpful in reducing your energy bills.

The biggest concepts are air sealing with testing, and mechanical ventilation. All the other sexy stuff like tiny mechanical equipment, Earth tubes, HRV/ERVs, massive insulation levels, etc... only become effective when air sealing with testing and mechanical ventilation are taken care of first.

What I would do: Insist your architect shows how the air sealing is to be done, especially around windows, doors, and any place the air barrier changes material, direction or planes. These drawings need to be included in the plans. Insist your contractor follows those drawings. Insist on having the house tested for air tightness with a blower door test (pressurizing and depressurizing the house). Typically this should be done three times during construction, once upon initial completion of the air barrier, again when all known holes through the air barrier are done (windows, doors, electrical, HVAC, water, etc...) and once again at completion. At completion a house done very well will have passivhaus levels of air tightness which is 0.6 Air Changes per Hour at 50 Pascals of pressure (ACH50), Well built houses will be about 1 ACH50. I would highly prefer all HVAC equipment to be inside of the air barrier (conditioned envelope really). Insist that a Manual J calculation be performed by a competent engineer. I would also insist that the HVAC equipment be tested with a duct blaster (unless you go with ductless minisplits). I would also insist that the system be commissioned so that the air flows from the registers match what is called for on the manual J calculations.

07-03-16, 07:35 AM	#5
DEnd Apprentice EcoRenovator Join Date: Nov 2011 Location: NC Posts: 117 Thanks: 6 Thanked 27 Times in 25 Posts	Spiv, It sounds to me like you have a fairly low heating load. In that case for choosing equipment I would go for a heat pump over geothermal. I would also forgo hydronic in floor heat, simply because you seem to be in a mild climate. If you are indeed in a mild climate, I encourage you to look closely at the Passivhaus concept. If I remember correctly you already have plans drawn up? If so I doubt you can really go whole hog on a passivhaus but it's concepts are hugely helpful in reducing your energy bills. The biggest concepts are air sealing with testing, and mechanical ventilation. All the other sexy stuff like tiny mechanical equipment, Earth tubes, HRV/ERVs, massive insulation levels, etc... only become effective when air sealing with testing and mechanical ventilation are taken care of first. What I would do: Insist your architect shows how the air sealing is to be done, especially around windows, doors, and any place the air barrier changes material, direction or planes. These drawings need to be included in the plans. Insist your contractor follows those drawings. Insist on having the house tested for air tightness with a blower door test (pressurizing and depressurizing the house). Typically this should be done three times during construction, once upon initial completion of the air barrier, again when all known holes through the air barrier are done (windows, doors, electrical, HVAC, water, etc...) and once again at completion. At completion a house done very well will have passivhaus levels of air tightness which is 0.6 Air Changes per Hour at 50 Pascals of pressure (ACH50), Well built houses will be about 1 ACH50. I would highly prefer all HVAC equipment to be inside of the air barrier (conditioned envelope really). Insist that a Manual J calculation be performed by a competent engineer. I would also insist that the HVAC equipment be tested with a duct blaster (unless you go with ductless minisplits). I would also insist that the system be commissioned so that the air flows from the registers match what is called for on the manual J calculations.