New Build looking for green options
Last Post 05 May 2015 10:59 AM by BadgerBoilerMN. 5 Replies.
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NewcombUser is Offline
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22 Apr 2015 03:19 PM
My wife and I are just starting to plan for a house we expect to build in 2 years. We are looking to make an energy efficient home. Looking for ideas on what help make a house energy efficient. Ideas of the types of things we are trying to find information about: Air sealing the building shell Insulation types Roof Window types Led lights Building designs/orientation of house to benefit from sun. Solar power Tankless hot water heater Ac/heating options. Northern cal. Think 105 in summer, lows around 50 in winter. Anything else that might be helpful. Looking for resources, books, etc that might help. Thanks.
Bob IUser is Offline
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22 Apr 2015 04:34 PM
PHIUS.org is the home base for the US Passive House; the highest energy standard in the world, and depending on where you are, the cost to build to that level may be not much more than any other type of building. There are lists on the PHIUS website listing builders, designers, consultants across the country, so finding some in your area is pretty strait forward. I'd suggest you go to their websites & see what they are building and what they say about PH. Note that PH is a nonprofit organization; they train people in their methods and seek to spread the word so we can bring this country up to date with building technology. There are many builders using PH methods but not quite the same insulation levels, doing "net zero" or similar houses.

Basically it's about paying attention to things that most builders have been ignoring like thermal bridging, infiltration levels, insulation levels etc.

Also see the web site: GreenBuildingAdvisor.com

Good luck!
Bob Irving<br>RH Irving Homebuilders<br>Certified Passive House Consultant
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22 Apr 2015 05:07 PM
By 2020 all new homes in CA will have to be Net Zero Energy per CA Title 24.  If you're not building to that standard in 2017, it will negatively affect the resale value.  The time to figure out the most cost effective way for YOU to get there is now, while it's still in the design phase.

A few basics:

A heat pump water heater uses less than half the total energy than a tankless water heater. There are units out there right now that deliver an EF above 3.0. (Effectively 300% efficiency). That means 1/3 of the heat going into the tank came from the grid, 2/3 of it was drawn from the surrounding air.  During the cooling season the 2/3 of the heat that is drawn from the air comes directly off the cooling load. During the heating season it becomes part of the space heating load. But with a high-efficiency heat pump heating/cooling system those effects are somewhat muted.  But the PEAK draw of a heat pump water heater is miniscule compared to that of an electric tankless, and it's peak draws that drive the size & cost of the supporting electrical grid infrastructure.  When everybody has roof top solar, it's likely that the grid costs will then be assessed by "demand charges", based on the highest 15-minute or half-hour draw that a house is making from the grid during a billing period.  If/when that happens, a tankless electric hot water heater is a liability.  It's anybody's guess as to if & when residential demand charges get built into the rate structures in your area, but it's already the case for at least one utility in Arizona.

The shape of the house, and the size/orientation of the windows toward the sun makes or breaks the heating & cooling loads.  The more corners a house footprint has, the higher the thermal bridging of the framing, and the more exterior surface area there is per square foot of floor space.   If you can limit the footprint to no more than 6 corners, not a lot of ells or bump-outs, the better control you'll have over the heating load numbers.  If you can eliminate or minimize the amount of east & west facing windows, the better control you'll have over the cooling load numbers.  This is particularly true of west facing glass, since the unwanted solar gains occur during a much warmer part of the day, after the whole houses has been soaked in solar glare for hours.  South facing glass can be shaded by overhangs to allow seasonal solar heating in winter when it's desirable, but shaded in summer when the sun angles are much higher.

Keeping the roof lines simple, and orienting a major roof pitch for optimal uptake on rooftop PV goes a long way toward maximizing the site-sourced power per rated watt of PV.

A trussed roof with "energy heels" to allow for deep attic insulation, and keeping all ducts, air handlers, and other mechanicals below the insulation & pressure boundary makes it easier to air seal, and far cheaper to insulate.  If ducts & air handler are in the attic, it adds a lot to the cooling load unless you insulate at the roof deck, which is more complicated & more expensive.

From an overall lifecycle cost-effectiveness point of view, a good starting point is Table-2 on p. 10 of this document.  Note, those are "whole assembly R", after factoring in the thermal bridging of any framing etc, and not a center-cavity R. For example, an 2x6 wall with R23 rock wool batts comes in at about R14 after thermal bridging, not R23. Bump the stud spacing to 24" and use only single top-plates & window headers, etc and that bumps up to a bit over R15, but still well short of R23.  Add 2" of continuous rigid rock wool or EPS outside the sheathing as a thermal break over the thermally bridging framing, THEN you'll be at about R23.

Based on your temperature description you're probably in US climate zone 3, so use the row for Zone 3 in that table as your baseline.  But it may be cheaper to hit Net Zero Energy if you used the recommendations for Zone 4 (or even Zone 5), depending on your window area & orientation, and the cost of rooftop PV vs. the cost of higher-R assemblies.

http://www.energyvanguard.com/Portals/88935/images/iecc-climate-zone-map-energy-code-warm-moist-line-800.jpg


The size of the house also drives cost and R-values. A smaller house typically has more exterior surface area per square foot of floor area than a larger house, which will drive up the R-value requirements a bit to be able to hit Net Zero with a PV array that still fits on the smaller roof area.

With a high performance building envelope the heating & cooling loads can be quite modest- well below the output of standard HVAC equipment, much of which is sized for 1975 vintage code-min construction.  A high performance building envelope may not even need ducted heating/cooling solutions if the room-by-room loads are sufficiently low, and the efficiency of ductless air-source heat pumps ( mini-splits) has soared in the past decade or so, and are more likely to be a reasonable fit to your actual loads than other HVAC equipment.  And at that efficiency, the marginal costs of heating is less than condensing natural gas heating equipment (all of which is oversized for a high-R home.)

In your climate the peak cooling loads are likely to be higher than the peak heating loads, even though it is still a heating-dominated climate on a heating/cooling degree-day basis, so keep the focus on minimizing the cooling loads.   A typical 2500' house built to the recommendations in Table-2 of that BSC documentation will have a heat load of less than 15,000 BTU/hr @ 40F (the approximate 99% outside design temp of say Red Bluff or Redding), maybe even under 10,000 BTU/hr, but with a lot of west-facing window it could have a peak cooling load north of 40,000 BTU/hr.  But with careful window orientation & selection and optimal roof overhangs on the south side you should be able to bring it under 25,000BTU/hr, or even under 20,000 BTU/hr without it feeling like you're living in a dark cave.  If you can, use north facing windows for daylighting, since that has the least amount of solar gain, and also the least amount of glare & shadow.

A reasonably effective freebie design tool for this is the DOE-2 based BeOpt tool, courtesy of the US taxpayers.  There's a bit of data-entry to get the basic design in, but once it's there you can play "what if..." games to optimize the design fairly easily. 

There are many trade offs to be assessed in a new design. You can get decent advice about the particulars on this forum, but there are others.
JasonClarkUser is Offline
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27 Apr 2015 07:25 AM
If you want to build energy efficient house then few things should be kept in mind like you must see energy stars on products before using it. Heating and cooling also plays a very major role in it.
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05 May 2015 10:17 AM
Definately prime design numbers for a heat pump water heater, but the recovery is slow and you will have to be concious of demand.
Joe Hardin
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BadgerBoilerMNUser is Offline
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05 May 2015 10:59 AM
Posted By joe.ami on 05 May 2015 10:17 AM
Definately prime design numbers for a heat pump water heater, but the recovery is slow and you will have to be concious of demand.


Store more, since energy efficiency often changes demand in the "wrong" direction. Most want more for less.
MA<br>www.badgerboilerservice.com
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