Heat Loss and Manual J – PHPP and/or HRAI Manuals?
After looking into having heat loss/gain analysis done on my new house build I’m not surprised to see the costs coming in at $500 and up.
I am a Mechanical Technologist and have no problem with technical topics and math. As such, I have a hard time justifying paying other people when I can educate myself and learn how something is done. I generally prefer doing things myself anyway, that way I not only fully understand what’s going on, I also know the job is done right.
I already have the basic design of our house complete, and thanks to input from the Sustainable By Design website’s window overhang calculators I have what I think to be a decent looking house with very a good approach to window placement and shading.
I was wondering if a better Manual J approach for me would be to look at the Passive House Planning Package. It sounds as though it requires a LOT of information about the building envelope, which shouldn’t be a problem. Does the PHPP require information and inputs (data) that would not be accessible to the public? Like some sort of crazy detailed weather information? Just asking as I wouldn’t want to purchase it only to not end up being able to use it.
Also, I found an HRAI (Heating Refrigeration and Air Conditioning Institute of Canada) manual that looks very promising; Residential Heat Loss and Heat Gain. This is the technical manual that goes along with their course.
http://www.hrai.ca/technical-manual/residential-heat-loss-heat-gain
If the PHPP software is assumed to be WAY over even a reasonably technical person’s head, perhaps the HRAI manual would be a good option? Looking for input from those who have experience with the PHPP and/or heat design/analysis courses. Thanks!
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Replies
Lance,
If you have the time, you can master PHPP. Whether that makes sense depends on the amount of time you want to invest. The usual advice is, "Start with the nine-day training program. Then practice."
According to Jamie Wolf, a Passive House consultant, "PHPP is rigorous, comprehensive, exacting, precise, and to be used effectively requires a nine day training regimen or the services of a certified consultant."
GBA reader J. Chesnut wrote, "I work for a certified consultant and have gotten far learning the software in the process. The input for the PHPP is extensive and there are some difficult things to model like thermal bridging, inputting non-certified windows and ventilation systems, and other highly specific input like the thermal characteristics of the soil of the site. I think in order to maintain the integrity of designing with the PHPP certified consultants need expert support to answer technical questions as they arise. I don't think after the 9 day training that people understand all aspects of the calculations that the software is doing."
If you want to dive deep, you can listen to this podcast: So You Want to Be a Passivhaus Consultant?
With PHPP, there are three different U-factor numbers to enter for windows: U(frame), U(edge), and U(glass). It is very difficult to decide which values to enter for PHPP if you aren't using certified Passivhaus windows. So there are difficulties in using PHPP for routine American heat loss and cooling load calculations.
I depends on what your goals are. Unless it's a very high performance house (and even if it is such a house) freebie download tools such as Hot2000 or BeOpt are more than sufficient for estimating peak loads accurately enough to specify mechanical systems.
Martin, thanks for your thorough explanation. I was aware of the triple U requirement for PH windows, but for my purposes a "close enough" approach would be fine.
Dana, I will definitely check out those two freeware options, thanks!
I'm not going to pursue any specific type of building standard as a goal for this house, however certain aspects like super airtight construction will be aggressively implemented. Barring any significant weaknesses in my non-PH windows and doors, I'd like to shoot for as airtight as possible (seeing some builds exceed PH requirements there is inspiring). Also, with lots of insulation, proper solar orientation and properly shaded windows it should be a very efficient house. Let's just call it "Passive House Inspired".
My main concern with modeling is heat gain in the summer. Hopefully those modeling programs have a good grasp on window shading.
Lance,
If you want to do really accurate modelling of summer heat gain, accounting for shading and all that, I would expect a dynamic simulation engine like EnergyPlus (which is the engine behind BeOpt) would give you better results than the steady state model like PHPP.
I haven't used BeOpt, so I don't know if it gives you the inputs you need to effectively model your shading devices, but behind the scenes, EnergyPlus is definitely up to the task.
If you really want to get elaborate with modelling shading, you might look into NREL's OpenStudio software: https://www.openstudio.net/ which is another piece of free (paid for by your tax dollars!) software that also uses EnergyPlus as the engine. It allows you to model your geometry in Sketchup so that you can do really accurate multi-zone simulations accounting for all your window shading and whatnot. It's more geared towards commercial construction however, so BeOpt may still be the best choice for residential simulations.
You might check out Unmet Hours: https://unmethours.com/questions/ for Energy Modelling specific questions (in addition to GBA of course).