Putting Passive House to the Test! Pt. 2 - Designing the Passive Bunkhouse

Just as in regular home design, a recreational vehicle trailer needs to be designed to fit the needs of the occupants.  When designing one from scratch you also need to take into considerations the rules and regulations that will govern the safe use of that trailer.

As part of the design of the trailer I will be talking with the proper Washington State agencies that oversee trailer creation and licensing.  I have purchased the latest code book for recreational vehicles, and will be referring to that for the plumbing, electrical, and fire codes that will dictate how the design goes.  Beyond those considerations I will be looking at materials, weights, and structural integrity.  I will run the design past a structural engineer to see if there are additional measures needed from their perspective.  Eventually I get to the pretty part and look at fixtures and finishes, but those decisions are a bit down the priority list right now. 

I have done some preliminary research into the road rules for a recreational vehicle – it can’t be wider than 8.5 feet and taller than 14 feet.  There are length rules that I won’t need to worry about because I am not building something extremely long, but if you decide to, do look into that.  I know the WSDOT (Washington State Department of Transportation) will be one of my next stops to get all the steps they need me to take, but first I wanted to have a preliminary design to show them.  I figure it wasn’t necessary to start the discussion, but a drawing might trigger additional information and thoughts that might not be there if I just walked in with a “I’m building an RV – what do I need to do?” question. 

My design criteria was that the RV had to be smaller than the 52’ mobile home that currently is on the lot.  It is a very tight lot and I want to have room to park on the lot and not at the road.  I also didn’t want to have something unwieldy to tow.  Finally I wanted to see if I could design something that was in a fairly common travel trailer size bracket and if it could end up meeting the Passive House requirements.  I have not run any simulations yet so it will be an interesting experiment to see how it performs. 

While looking at different design possibilities I came across a very interesting website about a RV park model product called the WheelHaus http://www.wheelhaus.com/. (Which reminded me of the Rolling Huts that OSKA Architects designed http://www.olsonkundigarchitects.com/Projects/825/Rolling-Huts#) They both have a way to make a small place seem large and provide a lot of light.  Since pointing that large end window towards the lake would be ideal for a view as well as Southern exposure, I knew this was the design I wanted. 

About the same time I saw the WheelHaus park model I watched a documentary about designing an extremely tiny apartment.  One of the things they mentioned was that in order for a tiny apartment to not feel tiny the ceilings had to be at least 9’ tall.  When I heard that it made the WheelHaus idea click – that ceiling was not only really cool to look at, it would make staying in a small RV so much more enjoyable.  With that in mind and the knowledge that I could have an RV 14’ tall I came up with the following 200sf plan. 

Because I don’t have the exact dimensions of the flatbed trailer this will be built on, the ceiling heights are all rough estimates.  I will take the blog on a field trip next week to visit a trailer sales lot to see the different options I can use as the foundation for my new RV.  There will be pros and cons for the different styles, just as there are for regular home foundations.  Ultimately the deciding factor will be what can give me the most room, but still allow for holding tanks to be placed to code underneath.  Once I have decided on the trailer the design with material selections can begin and I can also talk to the state about their requirements.

But first one last thing to take care of – what to call an RV built to Passive House principles?  I thought I would tie the new trailer into the history of the lot it will be parked on.  One of the buildings that will be removed was referred to as “the bunkhouse”.  When the family would come to camp they would stay in the Mobile Home, but the boys got to camp out in the bunkhouse.  The idea of having an actual bunkhouse made me smile when I first heard it and I have decided that this project will be called the Passive Bunkhouse.

Up next – Road trip to check out trailer styles.

Putting Passive House to the Test! Pt. 1 - Introducing the project.

Remember when we were kids and discovered the cool effect you got when mixing vinegar and baking soda?  It was like we discovered the secret to making our own Volcano.  It’s been many a year since I made a baking soda Volcano with my own kids, and now I get to put the old lab coat on once again and mess with science (or make a mess of science!)  Either way, you can follow along in this new series “Putting Passive House to the Test!”.

I recently bought a small lot on a lake in a Marine 4 climate.  There are actual Temperate Rainforests in the area and I wouldn’t be the least bit surprised to find out my lot could be considered one too.  I have one shed that is almost toppled over from the weight of the moss on top.  The other two buildings have molded and all will be demolished soon to make way for new buildings.  Since I don’t want to worry that my new buildings will suffer from the same fate as the old ones I wanted to try all the science that I had at my disposal – the Passive House Planning Package (PHPP), the 2d heat transfer modeling program THERM, and the moisture migration software called WUFI as well as monitoring devices to plan my project well. 

Since unusual climates have garnered some attention in the Passive House community I wanted to find a way to make my project into a test bed so that we could all learn something together.  Because of that I will be inviting anyone with an opinion or question about Passive House to join in the discussion and make comments or suggestions to these articles.  I will be designing and having built a Recreational Travel Trailer and two small out buildings.  I want to use Passive House principles in their designs and monitor them for moisture.  Because they are all small I don’t know if they will meet Passive House criteria, but I am certainly going to try!  I want to use the usual materials and some unusual materials or products to give those a chance to be tested as well.

As I design and make choices I will be discussing them here in the Small Planet Workshop Passive House blog.  I’ll tell you what I’m doing, why I make the choices I do, and about the different materials and methods I am considering.  The first project will be the travel trailer and I already have some material ideas – vacuum panel insulation the Small Planet Workshop wants to test out, and a really cool HRV that the guys at http://www.foursevenfive.com/ carry.  One of the small buildings will also be designed with another new product that the Small Planet Workshop wants to try out (Albert is always looking for those good products for y’all!)  I’ll tell you about that when we get to that building’s design. 

The other small building will be one I want the Passive House Community itself to design.  We’ll be building each wall, ceiling, or floor section from different assemblies so that we can test as many options as possible.  This is where I want you to put your thinking cap on.  Is there a wall system or product that you would like to see used in a Passive House construction to see how it performs?  Tell me about it.  We’ll gather all the suggestions and recommendations together and take into consideration all the reasons people give for the items or methods they are curious about so that we can answer as many questions as possible.  Start posting them as comments here as soon as possible!

I’m sure this will be more fun than a baking soda volcano, and hopefully the excitement will get the Passive House community talking and sharing ideas while I mess with science and help me NOT make a mess of science!

Up Next – Designing the trailer.

The ABC's of the PHPP - Part 20 Crossing the Finish Line

Last week we worked through the last PHPP worksheet for a Passive House project.  Now we look to see if we made the final requirement for a successful Passive House project – do we meet the Specific Primary Energy Demand requirement of 120 KWh/(m2a) maximum?

Let’s assume that we got close, but we are not yet there, but a few tweaks could make the difference.  Perhaps we are off by a lot which might indicate either an unfamiliarity with low energy usage or more likely a really glaring typo.  Go back and look over the worksheets that feed into this number.  By now you should be familiar with what each one is set up to measure and this can give you ideas for optimizing or finding that typo.

Let’s start with the DHW & Distribution worksheet.  Did you accurately measure your hot water pipes?  What happens if you change the insulation on the pipes or the location from a cold region to being inside the thermal envelope?  Can a design change to re-route the pipes effect the performance?

On the Solar DHW worksheet make sure you accurately modeled your system.  What if you increased the amount of solar hot water you can provide?  Any water heated this way will be automatically deducted from the PE value demand of water heated with your energy carrier.

The Electricity worksheet is where you listed your appliances and electrical usage.  Did you properly declare all the appliances?  Are they listed in the right location of either inside or outside the thermal envelope?  What happens if you move them or change the way you expect to use them?  Would you use the clothes washer with just cold water or will you hook it to the DHW?  Can you replace the dryer with a drying closet and re-route an exhaust port of your ventilation system to draw exhaust air through the drying closet?  In the upper right hand section of this worksheet did you declare the type of energy carrier you will use for your domestic hot water and space heating?  If not, the PHPP will assume you are using electricity.

The Auxilliary Electricity worksheet takes into consideration all the pumps and defrosters that keep the systems working.  Even if you are providing your DHW through solar means, the pump needs to be listed here if it is electrically powered.  Did you properly list the power needed for each of the different pumps & defrosters?  Could you substitute a more efficient one to make a difference in the bottom line?

The IHG worksheet doesn’t have many inputs itself, but it does get information from other worksheets and one of those is the Electricity worksheet.  You have the ability to add undeclared electrical usage that might be unique to your project in the “other” section.  This gets referred to the IHG for calculating any interior heat gains.  If you know you will be using an electrical appliance that needs to be declared, be sure to list it so the heat it generates is also considered in the operation of your project.

The Compact worksheet is affected by the coefficient of performance of the system you are using for your heat pump.  What happens if you use a more efficient system?  Did you remember to enter the information about a subsoil heat exchanger to pre-warm ambient air to help defrost the SHX if your project is using one?  Don’t forget to record any solar DHW used for space heating on this worksheet too.

The District Heat worksheet only has space for solar used in heating (don’t forget to record that if you are using district heat!) as well as the Utilization factor of the heat transfer station.

The Boiler worksheet needs to know what energy carrier you are using for your boiler.  This could impact your PE value depending on what type of energy you are using.  You can try changing from an oil based boiler to another type and see what it does for your PE value.  Be sure to mark the solar hot water value on this worksheet if you are using that in conjunction with a boiler.

That just leaves us the PE Values worksheet.  You can see that each of the sections focuses on the efficiency of the mechanical use and the energy carrier.  Be aware of the equipment that is available to assist you in efficiency.  Also notice that the last section of this worksheet has a place for recording the amount of energy that is generated by Solar Electric panels.  If you are generating power this way the Specific Primary Energy amount will be reduced to reflect you not having to bring energy to your meter.  Passive House requirements do not give use credit where you can then use more electricity because it is technically “free”, but it does consider you did not haul that power with resulting losses from a distance.

If you have gone through all the worksheets and are still not quite hitting the mark – give it another look.  The more you understand the PHPP and what it is designed for the more you will be in tune with where you can make changes or look for errors that you might have made in entering information.

I hope you have found this series on the ABC’s of the PHPP useful.  Up next I will be discussing humidity, moisture, and a project that I am designing that will be in a Marine 4 environment that is practically a temperate rain forest. 

The ABC's of the PHPP - Part 19 PE Value - The big Finale'

The PHPP manual introduces the last worksheet that we are examining in this series this way: 

“PE Value” Worksheet - Calculating the Primary Energy Demand and CO2 Emissions

The PE Value is a key requirement in meeting the Passive House standard and being able to have your project certified.   Let’s quickly review what is the criteria that you must meet for PH Certification:

Specific Space Heat Demand – max. 15kWh/(m2)

  Or Heating Load (alternatively) – max 10 W/m2

Blower Door Test results – max .6 ACH at 50 pa

Specific Primary Energy Demand – max 120kWh/(m2a)

In the beginning of this series on the PHPP we went through the steps to meet the Specific Space Heat Demand.  Next we talked about the blower door test that you will do at your project once it is under construction.  Now the process has taken us to the big finale’ - The Specific Primary Energy Demand.  This is where the type of energy that will be used and the impact it has on the environment is considered.  This is where your project’s planned ability to add CO2 to the atmosphere is capped. 

Passive House planning takes into consideration the total energy that is required to provide for the actual energy that you use.  They add the impact of generating that energy, the amount that is lost through the physics of transporting it to you, and then they consider all the energy that you will use to heat, cool, ventilate, and run your home.  Even in the Pacific Northwest where we have quite a bit of electricity generated from Hydro Electric dams, there will be more energy created than what your household is asking for so that it can be delivered to you.  

As electrical energy is transported across electrical lines some is lost through transmission.  As fuel oil is shipped, other fuel must be used to transport it after even more fuel is used to extract it.  The PHPP is so sensitive to the concept of reducing energy usage that it will consider what your energy carrier is (the type of energy fuel source) and calculate how much additional energy is needed to enable that fuel source to provide energy to your house.  

You will notice that the PHPP talks about Primary Energy Demand and Specific Primary Energy Demand.  They sound a lot alike, but they are different.  Primary Energy Demand is the energy that YOU use to operate your house.  It is the amount that is delivered through your meter.  The Specific Primary Energy Demand includes that primary energy that was delivered through your meter AND the energy it took to create and bring that primary energy TO your meter. 

In terms of carbon footprints, the Specific Primary Energy Demand is a large dark carbon heavy footprint.  What you actually use to run your household is smaller and one might think more environmentally healthy footprint, but you are Specifically responsible for the larger carbon footprint.  So how do you have a more environmentally healthy footprint?  You reduce your energy usage so that less is required to get what you need to you.  When you do that the environment benefits and you benefit too.  That’s one terrific Finale’!

The ABC's of the PHPP - Part 18 The Boiler Worksheet

Gas Boiler. Public Domain image.There are many ways to heat your home and your hot water.  This sheet is for recording the use of a boiler that can be used to do both. 

I am used to a household hot water and furnace system being 2 separate systems that might even use 2 different types of fuel to do their heating.  Currently I live in a house with a gas hot water heater and a gas furnace.  Others may have an electric water heater or heating system.  Still others may have a woodstove that burns wood or wood pellets.   Boilers can do the work of both a water heater and a furnace.

A boiler makes use of some type of fuel to heat water that can be stored in a tank for domestic hot water use or distributed to a series of radiators or in floor heating tubes for space heating.  Even solar hot water can be included in the heat source of a boiler.   A separate calculation is needed to determine how much the solar system contributes to the overall hot water supply.

On the Boiler worksheet you will need to determine how much of the water heated is to be used for DHW and how much will be used for space heating.  You will need to declare how the water is being heated (oil, gas, wood, pellets, etc.) and the performance data of the equipment.  You can give the exact performance numbers or use a default set of numbers that conform to DIN V 4701-10.  Check with your boiler manufacturer for accurate numbers as the default are based on minimal usages.

You will see that there is a section for oil and gas boiler inputs and one for Biomass which would be where you would list your wood or pellet boiler information.  The PHPP manual strongly recommends using actual manufacturing specification information to obtain the best results on this worksheet.

Next up – we tie all this together in the PE Value worksheet.