Energy Calculations

[taharvey]

I've only been using Energy-10 for a couple months. But what I learned from using it has *really* improved my understanding of where efficiency gains are made. I think most of us are designing in the dark, and very few people know where to put money/design resources to get the biggest returns. And the places that most people think often have the least benefit.

Code or not, I think all architects/builders/designers should use such a tool on all projects, and I dare say it should be mandated. Energy use is big deal, much bigger than many of the comparatively irrelevant stipulations required by code.

[Jorge Araya]

In California the software must be approved by the CEC California Energy Commission!

[frwillia]

Originally posted by taharvey
Code or not, I think all architects/builders/designers should use such a tool on all projects, and I dare say it should be mandated.

That SW looks to me to be a loooong way from being something that should be "mandated". There is way too much stuff being "mandated" with too little understanding of the long term consequences.

The government requirements that are currently in place define the results required and furnish a program to verify meeting the results - the process to get there is left up to the designer. I like that a lot better than some legislative entity telling me I have to use Energy-10 to design my house because they know the results of applying a show box model to all structures will result in whats best for everybody.

Reading the WEB page on the SW, it looks like a good training tool but its modeling capabilities are so limited I am not sure how accurate the results will be in predicting energy cost - and its nearly impossible to know how accurate it is because there is no reference against which to check it. As a qualitative tool or training tool, it has promise. Not sure beyond that. It takes more than qualitative understanding to achieve a definable optimum in some sense.

After decades of engineering practice I can say confidently that the devil is in the details - especially in modeling system performance. At the moment we are not having any trouble meeting the prescriptive limites of the code or the energy rules as applied here, so spending $300.00 to model a shoe box that may or may not produce accurate data for the house being designed isn't going to happen any time soon.

If you are having trouble meeting the local requirements it could point you in a direction as you say, but in terms of modeling the vital details of the structure under design, it looks incredibly limited.

On the plus side, its apparently a work in progress with a lot of development taking place that might eventually result in a tool for modeling the building geometry as more than a shoe box.

On the minus side, there are several government agencies involved which frequently means a lot of turf battles and political friction. There is, for example, quite a bit of controversy about some recent energy "mandates" that indicate they aren't really a good idea and are in fact counter productive in energy terms.

When I designed our house I had some things I wanted to accomplish:

1) Natural gas (lighter than air) was not practically available at the site and I didn't want any propane (heavier than air) in the house.

2) I'm retired and did not want to be subject to the random fluctuations of heating oil prices, or to have to buy and maintain such a huge potential polution source as a several hundred gallon heating oil tank. They are ugly as a mud fence above ground and bot expensive and a definite hazard below ground.

3) Burning coal wasn't in the cards either.

4) There isn't a lot of sun here in the winter (climate zone 11) so solar heating was going to get really expensive - limited budget.

So we insulated the bulding envelope to code or above (where we could) and installed a closed loop geothermal system with a 4 zone control system.

I did model the house in HVACalc - and did some parametric studies by varying the wall and ceiling insulation - that resulted in sizing changes which could be translated to capital and operating cost, at least at today's prices. I didn't do a Montecarlo statistical analysis of weather and envelope variations - that wasn't going to be done with HVACCalc as the building modeling tool in any reasonable schedule. Extreme value analysis was clearly not the right choice and using the recommended design temperatures for the region looked like the best bet. Although, the weather data that is apparently available on the Energy-10 disc might be useful as input to such an analysis if one had the right model.

But frankly as near as I could tell, if I did a good job of sealing up the house, installed an energy recovery ventilation system and a closed loop heat pump, met the local code requirements for windows and insulation, I'd done about all that was cost effective under the current state of knowledge for my use of the building.

I also had a professional model the house as a sanity check. After going over their model with them, I had to fight with them to keep them from making the heat pump too big just to cover their behinds.

I'm not all that impressed with the professional's HVAC design products. I think they are trained right but there are market pressures that push their recommendations in the wrong direction (over size - which is really a bad thing especially for air conditioning). That isn't going to be changed by Energy-10 - it will have to be changed by making a change in the business/design/liability environment that they operate in.

The HVAC system works just fine so far. The sewing room, which is over the garage, has R38 insulation on the roof and under the floor (which is over an insulated but unconditioned garage), R-19 on the walls. It needs a bit more cooling than the rest of the first and second floors. The basement has R12.5 walls and requires at least a little heating even on the hottest days so far. The 4 zone heat pump system will cool the above ground floors, switch over and heat the basement as required, then go back to cooling as required for the above ground floors.

The energy recovery ventilation only operates when the heat pump is operating so that humid summer air goes through the cooling coils to get dehumidified as it comes in.

Once the sizing was right, the professionals did a first class job of installing and tuning it.

Everything in house design is a trade off - an attempt to find a balance between competing requirements. There are "always" competing requirements. It is much more difficult that is at first apparent to mandate things that actually result in a long term improvement, especially in complex systems that are operating in what appears to be an equilibrium - to make a long term change requires establishing a new stable equilibrium condition between all the competing variables. This is not an easy thing to do.

Highly recommended, and affordable (thirteen bux on Amazon) reading that illustrates this in very understandable fashion:

"The Logic of Failure" by Detrich Dorner, Rita Kimber, Robert Kimber.

Fitch

[James Eggert]

Fitch Very nicely put!

"I had to fight with them to keep them from making the heat pump too big just to cover their behinds."
This is why I purchased my own software, in this case HvacCalc, to perform the accurate calculations I needed for ICF houses. Although, the heating side can be oversized without too much impact, the cooling side of the equation is terrible when the old school sizing or seat-of-the-pants sizing is implemented! That is why I spec what I want for cooling tonnage, and I will not allow any more than a 1/2 ton contractor compensation factor. This way I make sure the system works hard when it needs to!

[FWD]

Great reply Fitch. I think energy conservation is important but I think with all the insulation,low e,dual glass, etc. req. it eems no calcs should be needed on small
minimumly glazed projects to make it energy efficient. I don't do calcs but have heard where input data was fudged just to make it pass.

[RMorrison]

Originally posted by James Eggert

Although, the heating side can be oversized without too much impact

Actually, it CAN be oversized with a major impact if you're using a high-efficiency "condensing" furnace. Frequent cycling of the system causes a signficant loss of efficiency.

[Alex-Berkeley]

Richard is right on target vis-a-vis system oversizing.
In the energy conservation biz, the problem really isn't with the design and documentation of of energy compliant houses ... it's with the implimentation in the field. Years of monitoring and observation are resulting in an emerging profession of energy inspection professionals (HERS raters).
In California, its very likely that more than 75% of all construction in the next 4 years (which covers 2 cycles of state energy code revisions) will require inspection from a certified Home Energy Rating System inspector. These inspections can cover everything from proper insulation installation to duct pressure testing.
Sure, this is going to cost the builder more ... but what about the home buyer who has a right to expect his building to perform to code?
BTW, California Chief Users ... big changes are coming October 1st ... don't get caught by surprise especially if you work in a Cooling Climate Zone (2,4,10-15)! The new standards weight your energy use by the time of day that you use energy (TDV) ... a house in Zone 12 that doesn't carefully consider cooling design features will be very difficult to permit. I'd suggest you take a standard project that you may have done in the last year and have a CABEC certified energy consultant check it for you under the new 2005 standards using either Micropas or EnergyPro (beta versions only).

[James Eggert]

Richard
You're right and I knew my general comment would be taken to task. The heating side can be a problem when short-cycling just as the cooling side does, but in the case of your example, super efficient units with condensing flues it is a very bad practice to short cycle the heating unit as it never really reaches it's efficiency.

Alex
I'm aware that permit costs for building in CA are so out in left field compared to the rest of the country I'm surprised there isn't a lynching in some town EVERY week. One of my $5000 permits costs about $40,000 last time I heard! And now they want to add on another layer of buoracracy?(spelling?) The intent to hold down building while at the same time making people build to absurd legislation is mind numbing! I know that CA finally decided to adopt the IRC2003 and not the fire code, FBA I think. I know they, like other states will also have ammendments and changes they feel necessary! Good thing they went with the IRC though, because they were the only one in the country with their heads in their a....
And now they want to add another layer of intrusion, of course for a fee!!! We build safe, energy efficient houses in the Northeast but we don't legislate to such an auspicious point! we have a few amendments too, but not what CA appears to think they need?
What I don't understand is if CA builds to a code similar to ours, technically a minimum safety code, and allows for the seismic costs, how the fee structure for permits itself was allowed to escalate into the stratosphere ???? This fee structure must of been rammed down the builders, contractors, owner, commercial entities, etc one day when the whole state was on vacation and didn't vote on something!?

[taharvey]

Fitch,

Energy-10 is meant for design not training. The reason for the shoebox model with a 2 zone heating system limit is that is all that is required to get within a reasonable degree of accuracy for most residential homes unless the design is very large or complex. I've talked to a few engineers, and the energy-10 calcs come within 2-4% of full-model CAD export calc on energy-plus or DOE-2.1 - which are a lot more time intensive.

But there are two different kinds of accuracy, accuracy of the house description and accuracy of the model comparisons. Nailing the house description is always imperfect but if you can get within a few percent, that does the job. However, more important is accuracy of the strategy comparisons, that is where Energy-10 is dead-on. This is how you can see exactly where your money is best placed to get the most benefit.

Energy-10's simulations are not simplistic linear calculations. It uses DOE-2.1 plus some other engines to actually simulate the whole house for a whole year based on a weather file generated from a local 30 year climatic history. It simulates everything from the convection in the wall insulation, to HVAC, to the heat given off by the occupants, the lights, and appliances (and the daylight offsets to those light) based on typical weekday/weekend occupation schedules which are selectable by type of building. Though it is thorough, its easy to set up because it has well researched defaults (like above schedules), though everything is editable in fairly short time if you need different. This whole system simulation is important because everything affects everything else - and there is a sweet spot in all projects, the win-win-win scenario.

But frankly as near as I could tell, if I did a good job of sealing up the house, installed an energy recovery ventilation system and a closed loop heat pump, met the local code requirements for windows and insulation, I'd done about all that was cost effective under the current state of knowledge for my use of the building.

Could be. But I consider myself well educated on the subject, and found my self surprised at outcomes. For instance, take the standard advice to add insulation to the roof. Several house simulations in energy-10 show this to be a waste of money in many cases. If you have 16"OC 2x6 walls with R-19 batt your whole wall is only R12. All the insulation in the world (R-30, R-40, R-100) in the roof will be a complete waist of money, because your wall losses far outway the roof. You should put that money into better walls/windows.

There isn't a lot of sun here in the winter (climate zone 11)

Don't know what you mean by zone 11. But I assure you that nearly all climates have fair solar access. Again this is why simulation is important. Just for perspective: Maine, Minnesota, and Washington have 2/3rds the annual solar access of the best location in Arizona. Not 1/10th or 1/4th, but 2/3rds! Also, all homes are solar homes, it's important to actually understand to gains/losses and the implications to energy use.

Example: I just designed a house in the mountains of Utah 9000 Ft elevation, winter 7-8 months of the year, 6ft. of snow 6 months of the year. Started with conventional building parameters and >$150/month energy bills. Iterated through many variations in energy-10 until it was near net-zero energy use. Essentially $10-20 of heating/cooling a year. How much did it cost in extra construction? Not much, with the cost of HVAC offsets maybe nothing. And no you couldn't ever tell it was a "solar" house. Just the right type of insulation, sealing, mass, and windows to the design, with no esthetic changes.

Great reply Fitch. I think energy conservation is important but I think with all the insulation, low e,dual glass, etc. req. it seems no calcs should be needed on small
minimally glazed projects to make it energy efficient. I don't do calcs but have heard where input data was fudged just to make it pass.

The problem is you don't really know, and neither do the sales people. Low-e glass? there are dozens of types. Which should you use? Don't know until you model it. Sure you can build something you know to be a better house than they built 30 years ago. But is that enough? What are the responsibilities of a designer? Like it or not you're not just designing homes, they are also mini power plants (or energy dumps)- and the implications of your choices will affect the occupants and society for decades.

[Glenn Woodward]

You guys might be intertested in what we have in place in New South Wales, Australia.

http://203.110.153.11/information/about.jsp

We need a BASIX certificate with the submission of every dwelling.
The aim is to reduce water consumption by 40% and reduce green house gas emmisions by 25%, increasing to 40% in 2006 (from the average home).

[frwillia]

Originally posted by taharvey
Fitch,

Energy-10 is meant for design not training. The reason for the shoebox model with a 2 zone heating system limit is that is all that is required to get within a reasonable degree of accuracy for most residential homes unless the design is very large or complex. I've talked to a few engineers, and the energy-10 calcs come within 2-4% of full-model CAD export calc on energy-plus or DOE-2.1 - which are a lot more time intensive.

I'm still having trouble with the 2% - 4% accuracy of a two zone shoebox model as applied to all residential construction. I know houses where it would fit, I also know that it won't fit a lot of houses here.

My house has 4 thermal zones, each with its own thermostat and supplied by its own (on-off with a damper) duct work. The room over the garage (13' x 36' - my wife's sewing room) which is built with attic trusses, the second floor (32' x 40' x 8' ceilings), the first floor under the second floor plus the 8' x 26'x8' ceilings plus the laundry room/mud room area, and the basement which is 75% finished under the first floor (built with Superior Xi Walls).

I know from watching the controller while we are working in the house (I'm doing my own trim, paint, and flooring) that the 4 zones all take significantly different amounts of cooling/heating. With that data I don't see how one 2 zone model would come within 2% to 4%. Three zone houses are common here - the room over the garage (also common here) nearly always being its own heating zone.

I suppose I could model the house two zones at a time in Energy-10 (assuming I could get the zone interfaces modeled correctly), and eventually arrive at a series of 4 models producing data that that could be combined to be that accurate but that doesn't seem like its the best approach. I don't see any way to assume the whole house is in two zones (one model for the whole house) and get within 2%.

While I didn't use Energy-10, I did do some analytical experimenting. One of the variations I did using HVACalc4 was to model the floor platforms (except under the attic room) as seperate floors to see the effect of variation in rim board insulation. Rim board insulation has quite an effect. R21, which is the code requirement, works well though.

Another variation I did was to experiment with attic insulation using the same SW (the only HVAC related SW I have) to see if it made much difference. The code limits set in the IRC appear on the basis of that rather limited experiment to make sense. I agree - more didn't make much sense - so I didn't put more in there.

I did put more than the code required R25 under the sewing room floor - took that to R38 the same as the ceiling.

Additional wall insulation was going to be costly in my situation, so I didn't increase that.

We get more wind than one might expect based on the design wind (a healthy tree with a 14" trunk snapped right off in the yard across the road from me during the last thunderstorm) and keeping siding on over foam boards is sometimes an issue, so I didn't add extra foam to the outside of the house. I did design the house with all the required tie straps, over turning anchors straps to the foundation, floor to floor tie straps, anchor bolts, and then some.

My builder (my nephew for whom I design 8 to 10 houses/year) has never built an SIP house and I didn't want to be the first - so I went with standard construction - although I have the first house he did with Superior Walls (R12.5 insulation is built into the wall) - and I'm very glad I did that - it was the least expensive way to get mould free insulated basement walls. He had never done ICF, couldn't find anybody that had done it except one other builder that would only do it on houses where he built the whole house, so didn't do ICF walls.

The geothermal heat pump is incredibly energy efficient at cooling the house. Its literally pumping the heat down hill even if I set the thermostats to 65F.

However, based on your input, I'd at least consider using Energy-10 on a house if we design one where the two zone shoe box model will model the whole house. We may be designing some ranch houses that are on a slab (a house with no basement is unusual here - when they build on a slab mostly they put the main floor upstairs to get a virtual basement at ground level!) I might try it on them.

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On the California energy code changes. I frankly don't know if they make sense or not. CA has done some really stupid things related to environment - their gasoline formulation being perhaps the landmark of environmental stupidity. But that is off topic.

I moved there in 1969, and my eyes used to burn badly from the smog then. Stage 3 smog alerts were common in the San Fernando Valley then - and it would sometimes hurt to breathe. When I left last year I remarked that my eyes hadn't burned from the smog in several years and I couldn't remember the last Stage 3 smog alert, and it never hurt to breathe - so they have accomplished at least something good with all their rules.

My son in law (A vice President of Operations for KB Homes in So Cal.) mentioned the pressure testing of duct work and whole houses was coming. He didn't see it as a bad thing. He also thinks the building code and strict inspection is a huge benefit to builders like KB because it puts them all on the same basis related to quality of construction . KB can build a completely engineered code compliant semi-custom house (they have several floor plan options for each house) for a lot less per square foot than the small custom builder. If you build tens of thousands of houses a year there are volume related cost benefits.

When I went to the Contractor's Book Store on Canoga Avenue to buy my copy of the 2003 IRC (which was about to be adopted by PA) I couldn't help noticing that the LA County addendums to the UBC were bigger than the whole IBC! I never looked inside but on the surface it looked like LA County had rewritten the UBC.

I was also in So, CA for the 1971 and 1994 earthquakes. One of the interesting consequences of those quakes was to reveal what a shoddy - frankly fradulant - job of construction was being done by the home improvement building contractors. Block walls, that were supposed to have rebar in them had none. I mean zero rebar. It was in the plans, it was in the design, it was there when the inspector arrived, gone when the concrete arrived. Retaining walls had no grout - cement bags jammed in the holes half a block down so they looked grouted. Lots of short-nailed construction. "Almost" as bad as as an East Coast State that has been making news recently. <G>

I've been able to walk through the building sites of several of the major residential builders in So. Cal. Frankly I'm impressed by their code compliance and completeness. They have to be, they are major lawsuit targets because they have such deep pockets. The formed up slabs with shear wall bolts all bracketed in place, tied bar on chairs sitting there waiting for concrete to arrive are things of beauty. I've not seen one slab pour here, other than mine, that was even close.

In other areas the builders here may do some things a bit better. The drywall in my house is the best I've ever seen. You can't find a seam with a microscope. I did use high build primer on most of the walls but even the walls where I rolled the primer the seams are invisible. I couldn't say that about any of my three houses in So. Cal. The drywall here is smooth finish - in So Cal it was textured and you could still see the seams. My houses there were built by smaller builders - the drywall is better in the major builders houses.

My house uses PEX plumbing which I personally think is better than copper. It was legislated out of existance in parts of CA but I think it will be coming back. It was a union backed initiative to get rid of it - apparently its a lot less expensive to install.

Fitch

[taharvey]

Energy-10 certainly isn't the end-all. It would be great if their was "simluate this" button in CA that did the same.

By "shoebox" it doesn't mean the house has to be rectangular. Though anything more than 2 rectangles stuck together, takes a more time to enter. Ver. 2 this summer should fix that.

The nice thing that does set Energy-10 apart, besides being easy to use, is that you don't need a full blown CAD design first and therefore its useful for preconceptualization.

-----------------------------

As to my point about energy evals being required. Most of you are fine with following the IRC. And yet many things in the IRC a relatively arbitrary. Energy use actually seems worth putting in the code in comparison

[Alex-Berkeley]

"I'm aware that permit costs for building in CA are so out in left field compared to the rest of the country"

" The intent to hold down building while at the same time making people build to absurd legislation is mind numbing"

"What I don't understand is if CA builds to a code similar to ours, technically a minimum safety code, and allows for the seismic costs, how the fee structure for permits itself was allowed to escalate into the stratosphere ????"

Hey Jim,
Always great to get another perspective, but let me just fill in some answers.
I really don't have any kind of handle on what your permit fees are, and I know my clients frequently get sticker shock when they go into the Bldg. Dpt., but here's the facts ... people don't want to pay taxes, simple as that, so when you need money for the schools, what can you do but assess a one time surcharge of $2-$4/sf for school fees ... the Proposition 13 movement gutted our municipal tax system and the governor can expropriate local taxes to balance the state budget. Don't misunderstand on the Prop 13 thing, homeowners were being hit awfully hard, but what the Prop 13 people don't talk about is that all the commercial property taxes were frozen, too. So backing away from the sensitive issue of property taxes, etc. the municipalities have no other choices to cover their operating costs but to increase "elective" taxation items like permit fees.

And, boy, the permit fees, high or not, aren't holding down building at all ... there has been a tremendous explosion of multifamily housing ... and back to the energy codes, there are tax credits and federal loans that are dependent on beating the energy budgets by 15% as well as all of the Energy Star Programs ... you can't motivate the market with incentives like these unless you have a measurable, performance based energy code like you have in California. And as the production home builders are finding, buyers want some assurance that they are getting a performance product.

Actually, the energy performance based standards that we have in California were actually being developed by the Dept. of Energy in 1978 -1980 ... I was part of that project. However, the next president decided that it was better to drill more and import more fuel rather than promote conservation regulations... so he killed the project. California just finished the job (although, CA was working on a parallel system of conservation standards at the time.)

Have the regulations helped or hurt? Even the current governor is behind them ... because when you can manage the state energy demands by reducing load peaks, you keep the cost of energy down ... and more people can build and business can grow.

Whew!

(Sorry about the length, I rather be designing enery efficient, passive solar buildings....)

[frwillia]

Originally posted by Alex-Berkeley
And, boy, the permit fees, high or not, aren't holding down building at all ... there has been a tremendous explosion of multifamily housing ...

That is in the contest for understatement of the decade! They have run out of level ground in the LA suberbs and are flattening mountains into valleys to get room for 3,000 to 15,000 house developments. Just look in the Santa Clarita area within 10 miles of Magic Mountain. There are thousands (tens of thousands might be more accurate) of houses going up in just that area over the next two/three years. A finished lot barely bigger than the house, graded and ready to build on in some of those developments costs $150,000 or more. Frequently the lot is sitting where their used to be air or under a mountain. It takes big bux to take on that sort of development activity. They have platoons of lawyers and others working all the issues.

You would almost have to be crazy to want to take that on as a private person wanting to build a single house. There are people that do it, but I think they they are responsible for only a very tiny percentage of the houses being built.

-------------

If it matters: I voted for Prop 13 as a matter of financial self defense, and I'd vote for it again in a heart beat. The politicians didn't like it then, and they don't like it now. The politicians and others that have a vested interest in unaccountable tax revenue spent hundreds of millions to fight it, but it passed handily and with stood the court tests.

There will be a property tax revolt here in PA if something isn't done. PA is beginning to approach where CA was when Prop 13 got passed. Property taxes here are a "lot" higher than they are in CA. Any gathering of three or more adults ends up with property taxes in the conversation in a surprisingly short time.

---------------

I heard all sorts of grousing about how the building code would kill the construction here in PA too. It hasn't hurt the building business at all near as I can tell, and it has resulted in a noticable increase in the quality of the houses being built. The home buyers like what they are seeing in the new code built houses - and they definitely like the lower heating and cooling bills. I think before long there will be a price noticable differential between nearly identical pre-code and post code houses that is assignable to the difference in energy efficiency if nothing else.

Fitch

[FWD]

Good points Ta. Admittedly I just take what they give me and assume that this required minimal energy reduction package does what it is supposed to do.
But we recently purchased energy calc program and I should make that comparison. I have not taken much interest in that area and perhaps I should.