High efficiency envelope in San Diego

My wife and I are looking at building a second home in San Diego and I'd like it to be a high efficiency envelope. I know the climate is really temperate and in the target zone for sure. I'm thinking that in that area with a proper passive solar design we could get away without any air conditioning or heating? What kind of insulation profile are we looking at for this area?

Good evening San Diego! Its a very enviable climate. US climate zone 3, 2012 IECC wood frame wall minimums would probably be fine: (2x6) or 2x4+R5 insulative sheathing. Code calls for R38 ceiling minimum, I would recommend R49 especially if doing a vented attic. Where code is sorely lacking is the blower door test minimums (5 ACH@50). Aim for 1.5 for a more cost-effective level. All bets are off for fenestration minimums on passive solar but would stick close to them for non-south windows and avoid West and East windows altogether.

As to avoiding heating and cooling altogether, I have no idea. I think a heat pump water heater will greatly help the cause and I would probably plan on a mini-split if possible.

It depends greatly on the distance you are from the coast. If you can see the Pacific Ocean, the climate is moderated both in summer and winter as opposed to being even 5 miles inland. Further inland, like around El Cajon, you have much warmer summers and the possibility of frosts in winter. On the coast it is possible to go without air conditioning in the summers, but inland you would be miserable for most of the summer.

Mexicans routinely go without heat as well, and in Tijuana and Ensenada they use space heaters or more blankets and just make do during the winter. There is also a lot more concrete block construction on the Mexican side of the border and that gives their houses more thermal mass to help deal with temperature swings.

If you add in just a few elements of passive solar design, you will certainly be able to get away without A/C or heating. The typical house in that area only needs heat for maybe 4-6 weeks in the winter, and A/C for a few weeks in July/August. With that kind of heating/cooling requirement, even a "low to moderate" efficiency envelope is going to make for a comfortable house.

Hello Sean,

Here are some Green possibilities for you to consider. . . .

Breathable insulation made from natural materials —
hemp, sheep’s wool, cotton, wood fibre, cellulose and flax. It comes in many shapes and sizes with varying K values. Natural insulation is available as rigid boards, semi-rigid batts, flexible quilts and loose beads. It is a matter of selecting the right material for a particular application, and in that respect, it is the same as conventional insulation. - See more at: http://www.homebuilding.co.uk/advice/key-choices/structural/breathable-insulation#sthash.YV0eRtT9.dpuf

Using combed (cleaned and separated with a comb) wool as insulate batting would work well in your mild zone.
See these links for some how to ideas https://www.google.com/?gws_rd=ssl#q=using+wool+as+insulation

A straw-bale house with wool batting in the floor and ceiling would be even better than just remodeling a stick built home.



Breathable insulation materials list:


Sheep's wool --- K value --- 0.038 to 0.043 --- 180mm --- Thickness needed for U value 0.2W/m² (2)
Wood fiber --- K value --- 0.038 to 0.048 --- 180mm --- Thickness needed for U value 0.2W/m² (2)
Cellulose --- K value --- 0.038 to 0.40 --- 175mm --- Thickness needed for U value 0.2W/m² (2)
Hemp --- K value --- 0.038 to 0.040 --- 175mm --- Thickness needed for U value 0.2W/m² (2)

Hi Sean,

If this project goes down a more "main stream" architectural path, I would follow most of Brian's guidance. As he being a professional in the building trade he is well versed in the "code modalities" of general "stick building" and/or "contemporary green builds." I personally do not agree with many of these standards and concepts...yet...they are what they are...and...being built everyday.

Should the more "traditional-natural" building systems be of interest...Many here, can answer any direct questions that perhaps may rise. John and Jami thus far are in the "mindset" of what I would suggest.

You can probably achieve a "net zero" natural build in that area...or really close. I would go with either good breathable draft proof natural design light wood wall, perhaps a light clay straw timber frame infill "thick wall" design...or perhaps consider some of the "flywheel" affect heavy cobb, stone, or related moralities.

Great luck to you!

j

At the risk of creating more banter I wont feel good about myself today unless I defend my building envelope code prescriptions in response to Jay's comments. Perhaps I shouldnt have used the terms 2x as it certainly does imply a "mainstream" path.

The insulation minimums I mentioned are for wood frame construction which would be for timber frame or stick built.. There are prescriptive minimums for mass walls too but I personally feel energy performance will be better with the higher R values in the wood frame minimums.

I strongly believe that reducing monthly, un-renewable energy use should be at or near the top of permaculture values and goals. The current international energy codes offer some good guidance to achieving a minimal level of performance in regards to energy use and comfort.

Whether the build be mainstream or "traditional-natural" I urge people to achieve a minimum level of energy performance in their building envelopes in regards to air sealing, insulation and fenestration. A dwelling that is "traditional-natural" that uses mainstream amounts of un-renewable energy to stay comfortable, does not adhere to permaculture principles to me.

Hello Brian, et al,

As this being a "permaculture forum" the focus is typically going to lean toward "traditional and natural,"...and not...the conventional methods of CODE, industrial contracting...or the related concepts. Of course all thoughts are welcomed in the sharing.

We (those of us that work in the "building trades" professionally) know well what "mainstream architecture/contracting," would have us believe about...durability, R values, air tightness-thermal efficiency, etc. etc....a percentage of it I imagine is true....Yet, when I read:

Brian Knight wrote:...energy performance will be better with the higher R values in the wood frame minimums....

I must point out the countless millenia of "thermally efficient" mass wall systems that have very low R factors and rely instead on U factor and the "flywheel" effect. There are just as many Log Cabin, Rammed Earth, Cobb and related design/builders and researchers that can make similar claims. There is merit and drawbacks to any system...yet...considering the venue here...I am going to suggest looking toward natural and historical modalities to meet the goals of the architecture we discuss, facilitate, and describe as much as possible.

Brian Knight wrote:A dwelling that is "traditional-natural" that uses mainstream amounts of un-renewable energy to stay comfortable, does not adhere to permaculture principles to me.

I absolutely agree, and they never have to....if done well, with knowledgeable understanding, and attainable skill sets to facilitate.

Regards,

j

My favorite blogger of all, Tom at Do The Math, went through the winter of 2011/2012 without turning on the furnace in house that wasn't even designed for this:
http://physics.ucsd.edu/do-the-math/2012/03/home-heating-for-the-hardy/


I've never been to San Diego, but I gather that your goal is absolutely attainable. Without serious deviation from what most of us at Permies.com would consider just regular good sense.

You want to do the same thing in Manitoba, it'll be an extremely high hurdle in terms of attention to detail, expense, and unusual techniques. Accomplishing it in San Diego, though... I don't want to use the word easy, but... I'd feel confident of success if I were in your shoes.

Good luck and share your process with us when you start!

Mike

i would second light clay straw, or any other form of slip form building, thats what first comes to mind for the OP.

https://www.youtube.com/watch?v=iSApSrd8VwY

http://www.theyearofmud.com/2012/03/01/light-clay-straw-house/

other forms of slip form, using rocks, or wood chips in a similar way as light clay straw

http://www.motherearthliving.com/green-homes/2147484657.aspx#axzz39jpwayPx

The beauty of energy codes is that they do not dictate a type of construction. They only attempt to set a minimum level of energy performance.

Airleakage and fenestration being equal, a stone, adobe or rammed earth wall will lose heat roughly 11X faster than a similar thickness R50 strawbale wall.

Hello All,

I agree that "light straw clay" modalities have a great deal to offer this project. Also mixing perhaps some mainstream products like "mineral wool boards," and LSC...as welll as RE, cobb, with a timber frame armature all have promise.

Air-leakage and fenestration being equal, a stone, adobe or rammed earth wall will lose heat roughly 11X faster than a similar thickness R50 straw bale wall.

Brian, I don't believe this is either a "mathematical certainty," nor an "engineering fact," and based as much on statistics and assumption as many claims by the "natural build" folks. According to "mathematics and statistics" many things aren't what they actually are...like the Bumble Bee being able to fly. Rammed Earth, Log Cabins, Cobb, etc architecture do work...and work very well...learning more about these and looking at other systems and how they are measured...like in the U.K. as an example has both merit and worth. I believe that my "broad and esoteric" perspective is what allows me insight where other fields of view are perhaps a tad too narrow.

This project would benefit from an all natural build, as I believe many would, and any well planed and augmented elements of modernity could too perhaps be of worth if the fiscal budget supports it.

Regards to all,

j

The measurements of heat flow through materials is fairly established stuff. A material that is R1 will allow heat to flow through it 2X as fast as a material that is R2. This is why we insulate water heaters, fridges and coolers with high R insulation and not thermal mass. Can you imagine the performance of a cooler made with bricks? Same principles.

Most folks measure the performance of building envelopes by air leakage, insulation and fenestration. These are the big 3 variables that will impact how comfortable and efficiently a home holds in or keeps out the heat.

What about thermal mass TM? It improves energy performance but its impact is arguably small. Often times, thermal mass hurts comfort as it makes it more difficult to change the indoor temperature quickly.

What about thermal mass walls like cob, stone, rammed earth, and logs? As my quick statistic was meant to show, they can be a huge problem when we are trying to heat or cool a home or building. The only climates where thermal mass walls have been proven as effective as walls with insulation is where there is consistent, year-round temperature swings between day and night. While this can happen in all climates during certain times of the year, its very rare for a climate to experience this most of the year especially for the diurnal swings to bracket the 70 degree human comfort zone.

Oak Ridge National Labs has done the most cited research on the benefits of TM. The conclusion is that TM works best when enclosed completely inside the insulated envelope.
http://web.ornl.gov/sci/roofs+walls/research/detailed_papers/thermal/conclusion.html

Interesting the UK is being used here as a good source of building performance information because I often find very questionable things coming from there. For example, take the link in Jami's post. The title Breathable Insulation, is a bad start to me as "breathable" is arguably poor terminology because it has no agreed upon meaning. I offer more reasoning here in this blog: http://wncgreenblogcollective.wordpress.com/2013/11/04/should-we-eliminate-the-term-breathable-from-our-discussion-of-walls-and-buildings/

The opening sentence in Jami's link: "A breathing wall is one that allows air....... to move from the inside of the house to the outside." It then goes on to talk about the importance of airtightness of walls? Iam very confused by this philosophy if anyone can help explain it to me? How can a wall be airtight yet allow air to move from the inside to the outside?

When looking overseas for shining examples of energy efficiency, comfort and high performance building then its tough to beat what they are doing in Germany. PassiveHaus built homes use 90% less energy with NO renewable energy influences. They do this by paying strict attention to air leakage, insulation and fenestration.

Hello Brian, et al,

I am not belaboring the procedural methods of scientific testing, or outcomes of what can and are done in laboratories every day...and will continue to be. These, "are what they are"...and...we learn new and wonderful things all the time with them...including how wrong we are about things we "thought we knew," as well as, how narrow our view often has been on many things we had been "so sure about"...

Brian Knight wrote:Most folks measure the performance of building envelopes by air leakage, insulation and fenestration.

Many areas, even within their CODE systems, are looking at "draft-proof," and not "air-tight" as a better method of construction. Further, I would point out that the U.K. (to name just one) uses U factor not R factor in examining thermal efficiency, as they have a very dominated "mass wall" design in their vintage, and current housing stock. This is why cobb, stone, and brick are still in use there as well as, "infill" timber framing methods, both in restoration and new construction.

Paint with "narrow brush strokes," when describing modalities of measuring building efficiency can lead to narrowness of scope and understanding...There are many different and valid ways of assessing applicability of method. Many manufactures/facilitators in the "mainstream" building industry demonstrate "hubris" whenever a narrow parameter to anything is applied...especially when discussing something like "building comfort" or even the more tangible like, "what is efficient."

Brian Knight wrote:What about thermal mass walls like cob, stone, rammed earth, and logs? As my quick statistic was meant to show, they can be a huge problem when we are trying to heat or cool a home or building. The only climates where thermal mass walls have been proven as effective as walls with insulation is where there is consistent, year-round temperature swings between day and night. While this can happen in all climates during certain times of the year, its very rare for a climate to experience this most of the year especially for the diurnal swings to bracket the 70 degree human comfort zone.

It has also been shared many times that MW designs are too complex to examine with the same parameters as a high R value systems. When someone has built many of these MW designed structures, and studies them in depth over many years and speaks of their "challenges" I tend to really take note...yet not as much, when "faults" are reflected by others with little or no tangible knowledge of these building modalities, there historical application, and/or never having lived in one...let alone several; including more than one climate range. I agree, they may not always be the most applicable for a region...yet often the are, or can be made to be within environmental and economic logistical reason.

Again, the U.K. and other areas focus on U factor...not R factor in designing thermal resistance wall/roof systems. It really pays to be as thoroughly informed in both metric and understand their application when address the challenges with any thermal resistance system.

Many of us...more everyday...feel that "airtight" is not the goal in the way walls/roof assemblies should be designed...permeable (breathable for those that understand better this term) and draft-proof presents as a much better function to be aimed for. We are not designing "submarines or spacecraft," but homes and as such, they are extensions of the clothes we wear in a given biome. Breathable is always more comfortable a garment than none or slightly breathable attire. Wrapping houses in plastic and foam...then relying on more "technology" to make sure there is enough oxygen inside them to breath and not become polluted seems to be a move backwards to many...yet many "professionals" in the building field thinks this is a wise direction to move in...especially the materials industry behind the manufacture products that support them.

Regards,

j

Ufactor is the reciprocal of Rvalue. Most readers here are more familiar with Rvalue so I feel its the better of the two when discussing insulation properties on this forum. If there are readers here more familiar with Ufactor and want to know the Rvalue simply use this formula: U=1/R.

Windows are measured with Ufactor because they are a single unit made up of different components. There is a push however to start labeling windows with the Rvalue instead of its reciprocal Ufactor.

I strongly disagree that people are moving away from the idea of airtight homes. I think people are finally beginning to realize that insulation cant do its job if there is uncontrolled air leakage. Air leakage often contributes to unhealthy indoor air quality. Outdoor air introduction is the key to indoor air quality and there is less control over it when you have air leakage. Air leakage through insulation contributes to more moisture problems than the pemeability of the insulation.

Airleakage is different than permeability. Its tough to make to make a thermally efficient home with uncontrolled air leakage and you are more likely to have moisture problems due to humid air infiltration and exfiltration through interstitial cavities and moisture deposition on masonry or cold structural elements. Air leakage is the second biggest moisture concern after bulk water leaks like poor flashing.

All of these problems with air leakage is one of the main reasons that PassiveHaus has a minimum blower door test result as one of its only requirements. There is nothing unnatural about stopping uncontrolled air movement. There are many natural (and permeable) things that work. Stopping uncontrolled air movement is probably THE most important variable for a thermally and energy efficient home.

Again, I dont understand the explanation of draftproof vs airtight. What is the difference?

Do you know where in San Diego?

I've lived here for almost 20 years now. Last house was only 1 mile away from where I'm at now but in more of a valley and I really needed air conditioning.

Now where I live we only need it maybe 5 times a year.

By the way, I'm 6 miles from the coast. Last home was also 6 miles from the coast.

Last year we had an unusual winter but we had 5 days in a row of 28 degrees.

It is usually mild where I live but might not want to assume it always is. I went to visit someone 10 miles East of me this weekend and it was 15 degrees hotter.

Sheri