HVAC by the Manuals

First – a shout out to Martin Holladay,of the highly acclaimed GreenBuildingAdvisor, who gave us a “thumbs up” review. Since this may have resulted in some new readers, today I will put on my Sunday best and make sure to give you a blog worthy of this honor.

Indeed, our topic of HVAC manuals was inspired by a thread on the GreenBuildingAdvisor blog, “ Not all duct design manuals are created green.” It has become increasingly apparent to me that the ability to design proper HVAC solutions is one of the biggest hurdles to achieving widespread adoption of super energy efficiency homes. One of the readers, Whetstone Green, posted the recommendation of having a 3rd party specialist do the Manual J and Manual S (equipment selection). I wholeheartedly agree, as this would disaggregate the design and building science aspects from the sale of equipment. The poignant question is - where are these guys? See AirBalancing for some ideas.

In my need to know, I posed the questions posted on-line to my contacts over at ACCA, in their Technology and Research Division, and a few of my successful builder friends. What follows is a combination of my newly augmented information, with some of my thoughts – in hopes to shedding some light on the matter. Caveat emptor - I have not run these scenarios through the manuals – yet.

The key consensus was that the ACCA manuals are capable of designing for energy efficient houses, not just the average leaky house. The key is to avoid assumptions, and model the details. For example, Manual D will default to designing for the worst-case scenario - a good solution for the average leaky house client. For an energy house, reject the defaults and design for actual conditions. The manuals, and their aftermarket software, are just tools – the quality of the output is reliant on the operator input.

Step 1. Load – Base and Room by Room

Skylights change room design load

Determine the load for the building as designed. Energy modeling software used in conjunction with a drafting tool might help determine the point of parity for energy savings return relative to cost of additional thermal efficiency. Of course, the installation must live up to the modeling, or the rest of the equations are subject to change. Manual J can also handle this identification of load, and it should be done room by room, taking into account potential heat transfer of interior walls, windows, and skylights. For example, a partition wall between a mud room and a bathroom can be a source of cold transfer. Window exposures can also influence heat gain to a room, and relevant SHGC entered into the equation. Skylights may influence heat gain, but are also prone to leakage, altering the overall “tight” envelope.

Step 2 & 3 – System Choice and CFM Delivery
Once the load is determined, Manual S can help determine the best system. It can identify tolerances for equipment, as well as determine which equipment is best suited. This may be a choice between radiant or forced air, or even between different equipment components of the same manufacturer.

Manual T, and its new side-kick, Manual B are the up-and-coming power players. Manual T identifies how to select, size, and locate the supply air diffusers, grilles and registers for the optimal air distribution needs for a space. In a superinsulated home, for example with ICF walls, the exterior thermal envelope holds a relatively steady temperature and has a minimal convective heat loss. There is no need for a supply duct at the point of the wall, but the air does still need to be exchanged. This could be achieved with an air supply high on an interior wall, with the correct diffusor, saving on long duct runs.

The placement of ducts, and related total CFM needed informs the type of system to choose – thus the two steps are iterative.

Air Balancing

The newest guy on the block, the Manual B, is all about Air Balancing for both air and hydronic systems. And here is the crux of the matter. In homes reaching Passivhaus standards, there is little need for supplementary heating and cooling, and with no convective losses or air currents caused by envelope leakage, supplying air is pretty easy as well. But now it is like playing pianissimo in a concert hall. Every little bit counts. The balance is very fine. With small amounts of air being moved about, the act of balancing the pressures becomes the new testing ground. Jumper ducts join the fray.

Step 4. Finally –the ductwork.
This happens AFTER you have figured out how much air to deliver and where. The Manual D can help connect the dots. In an ideal (future) world, this will happen at a draft phase of design, to help transfer the flat drawings of Manual D to the framing plan, and adjust it to minimize loss of headroom, choose the best location for the equipment, and further fine tune Step 1, 2, 3, and 4. As mentioned above, use the tool to design all the loads, and there need not be any oversized ducts.

I’ve said it before – this is the field with the greatest potential for growth in residential construction. Who are these third party people? Will we evolve, as has the commercial construction, to defining a position of a “project integrator” who takes on this task, as well as the other complexities of interfacing green, structural, durability, smart home...? Not such a bad idea - time to start studying those Manuals!

The Business of the Craft

I love reading Fine Homebuilding. Its pages are full of smart contractors, who put great craftsmanship into their product, all managed with good business acumen. This is residential construction elevated to its finest, an industry which can be proud of its value.

Building is about anticipating - the needs of contractors who follow behind you, people who will use the house, the forces of nature – both as pertains to the construction schedule and the ability of the house to withstand the elements. Building is also about anticipating the amount of time needed for a project, the materials, the contingencies, the costs. It is about anticipating that work may come in spurts, and knowing when to work overtime to reap the harvest and to save for the lean times.

This is the potential and the hope for the residential construction industry. It is the profile of the Vermont builders and dozens of other exemplary builders across the nation. But it is NOT the common perception, based on empirical evidence. More common is the builder who overpromises, doesn’t provide accurate estimates, or is surprised when a 14 year boom is followed by a bust. It is the builder who seems surprised that the snow fell in December, or that building inspectors require ventilation for combustion appliances. Or the cabinet guy who says he is being rushed on a three week job – which was ordered 6 months earlier. But lest I digress (see Dec blog – Please Santa Bring me a few good contractors).

Our industry has only itself to blame, as it consistently fights any improvement in improving professionalism. In 1998, the Homeowner Protection Act was introduced to make warranty protection in new homes mandatory and require residential builders to be licensed and meet standards. Thanks to opposition from the home builder association, it doesn’t pass until 2007. And the intent continues to be sabotaged as the old boy network supports fraudulent representation of contractors “apprenticing” with uncles or buddies, still allowing rookies to set up shop with very little experience.

If we want respect as an industry, it needs to start within our own ranks. Run the business like a business, show up when an appointment is set, provide accurate estimates, and show craftsmanship in the work. Building cheap and cutting corners is not responsible, building durably and sustainably is. This is an industry which can start a recession if mismanaged, it is accountable for 50% of the energy consumption in the United States, and can make a greater impact on people’s lives than most any other industry. Are we up to the task?

“Build Tight – Ventilate Right”

This was the mantra chanted at all Energy Star / EEBA conferences for years to quell the concerns of naysayers who recalled the horrors of the “sick building syndrome” from the early 70’s attempts at sealing up office buildings. I joined the chorus of chanters, but in truth only really delved into the build tight part. But how does “ventilate right” actually translate into design?

This question of technical detailing become painfully pertinent as the results of the second blower door came in on my super insulated house. The first round was done prior to sheetrock, and was followed by several days of painstaking work in caulking, painting and taping to tighten up all the leaks identified by the thermal imaging camera. This baseline was ACH .39, pretty good for a remodel. This second round came at the project completion, and was anticipated to knock our socks off. Which is did, but with disappointment - ACH .35. Still very admirable, and just on the line of requiring ventilation, but certainly not a reasonable return on the investment of time and labor spent.

What happened? The house is riddled with holes in the form of exhaust vents which connect directly to the outside. All 7 of these bathroom fans are Energy Star fans, but this only refers to their energy efficiency in exhausting air. There is minimal protection in preventing unwanted infiltration when the fan is not active.

The solution? Heat Recovery Ventilators (HRV). All the bathroom fans can be fed into the HRV, which both prevents the problem of the unregulated holes to the outside, and also couples the amounts of air exhausted out of the house with return air brought into the house. This requires an HRV with a humidity control, such as the UltimateAir by Sterling Technologies, which has a 95% heat recovery, higher than US norm, and sufficient to meet PassivHaus requirements. The supply can to into the return side of the HVAC system.

Note that only a few HRVs have some level of humidity control, which can maintain existing levels, but are not able to reduce humidity.  Also, they can recover heat, but not generate it.  An HVAC system will still be required based on the climate, the insulation, and the size of the house.

Laundry and kitchen exhausts are the exception, as they must be vented separately and directly to the outside, per the IRC. Options for laundry are to install a condensing dryer, an outdoor drying line, or an indoor drying room with an exhaust outlet within the balanced ventilation HRV system. Kitchen exhaust fan covers can keep air from leaking in when the exhaust fan is not in use. The covers typically attach via magnets for ease of replacement.

The second portion of the air leakage was through some well-hidden gaps in the outer envelope. Once air penetrates the envelope, it moves freely about the rest of the interstitial space. And that is precisely why our construction methodology needs to move to panelized construction, or solid concrete. Wood frame construction just has too many opportunities for air leakage, too many workers who need to perform flawlessly, and too susceptible to change and shifts from the wood drying.

Build tight and ventilate right. My next project? ICFs / SIPS roof and HRVs. Overall faster, with more certain outcome, and less expensive than chasing air.

Capturing the Rain

Start with the end in sight, and expect the unexpected. (Stephen R. Covey). The best “end” for rain is to serve as watering for the landscape. The unexpected is when it lands in the basement.

Cricket to protect from snow shear

The roof design is the first critical decision. Simple “A“ frame roofs shed the water relatively evenly along the length of the roof. This is the easiest roof design to waterproof, as there are no penetration of pent-up water flow. The worst are the composite roofs with all sorts of extra gables, dormers, and pitches. Add snow to this, and you can get built up forces in the resulting snow and ice dams which can shear of entire dormers. They can be protected with “crickets,” which are designed to shear the snow to either side of the protrusion, like a chimney.

Dry "River"

The only other option is to not insulate your roof, and let the escaping heat of the house melt the snow. Not a very energy efficient option, but it should be noted that this may be the exact scenario in older houses. So before you air-tighten and insulate the attic, check to make sure this won’t be causing snow overload on the roof.

In warmer and drier climates, the roof can be used to capture the rain for irrigation purposes. A simple gutter works best when the roof edge is pretty straightforward. Collect the rain into a down spout, funnel into a rain barrel, or a dry river bed which is directed towards a garden area.

Scupper for Corner Valley Flushing

Indeed, rain capture may be a valid reason for some level of complex roof, such as a butterfly roof or a cross-gable roof, if carefully designed. Water can accumulate quickly in the valley. Wide valley flashing with an added “v” in the groove can help the water from splashing up the other side. But the biggest opportunity / problem area is the corner of the roof. Depending on the amount of rain, this can be a trickle, which falls close to the house, or a huge gush, which might shoot far out from the corner. Carefully designed and install a scupper to capture the water. The other risk with this type of roof design is ice damming, as snow melt makes its way down the valley, and may refreeze and start lifting the tiles as it backs up.

House designs have become increasingly more generic, and roof lines hopelessly complex. But rain and snow are two very good reasons to take a close look at the roof, and decide what “end” you have in mind before you start your design.

Interlocking Connections

Now that we’ve set our benchmark on the lean, rich and sexy level, let’s get down to the nitty gritty. In previous blogs, I discussed IKEA construction and air tightening. Let’s now take a look at a particular design and construction issue at the intersection of two well known “engineered” technologies and see how we might approach a solution.

ICF walls and SIPs Roof. Some years back, our colleagues at the NAHB Research center were sponsored by HUD to look at the detailing between ICF walls and SIPs. The hope was that a better connection system would be developed. A year or so later, the results were published as a PATH Initiative, essentially a catalogue of design details which were already used in the industry at the time, albeit vetted for structural and wind resistance.

While the attention and funding offered by HUD was commendable, I’m not convinced there were any really good solutions offered in this document. You see, if these connection assemblies worked so well, than there would be more positive reports from the field. But at that same time interval, I interviewed many builders who had tried the ICF / SIPS combo, and all spoke of struggles with that particular connection point.

So I’m tossing out a challenge. Can we take inspiration from the lock-tight mechanisms common in IKEA furniture, or the interlocking “snap in place” features common in manufactured goods? Is there a pair of brackets which could be installed independently on the ICF wall, and the SIPS panel which would allow the panel to sit, or catch on the wall to hold it in place while bolts lock it in?

And to up the ante, can we get a connection which has both positive structural connection, an airtight finish and no discontinuity of the insulation? And for those with cementitious skin SIPS – do all this – with no wood studs as splines, in order to maintain the fire rating. Besides, wood studs have been the bane of SIPS roofs, especially where moisture has migrated up into the peak of the roof.

And while I really don’t expect a solution on my desk by this evening, I do wish to point out that these are the very pieces that we are missing in our “green building” puzzle. I think the solutions will likely not come from manufacturers, or research centers, but perhaps sponsored industry groups including industrial designers, a few experienced and creative contractors, a building scientist and perhaps a structural engineer. That, and a few cases of beer.

Any takers?

Lean, Rich and Sexy

Add to this powerful and loved, and you have the top 5 hopes and dreams, at least judging by populist news media. Can these same themes be expressed in terms of architecture or housing? While this may not be the first descriptor which pops up when thinking of contractors or construction, I wish to challenge that paradox and propose that this is exactly the path we want to follow. Stay with me…

Lean - Think leopard, or marathon runners. The absence of fat replaced with well-honed muscles. The elimination of waste, in favor of increased value. Removing the “waste” in a house design means reducing unnecessary hallways or excessively cluttered rooflines, choosing instead to make efficient use of spaces, such as a dual function of a formal dining as an office. Lean builds in functionality: kitchen triangles which are just the right size, mudrooms and coat closets.

Lean is also the efficient use of energy. Not wasting the lighting and heat available from our free resources – sun and wind. Building a net-zero house, which reduces all energy waste, uses renewable energy sources where possible and only then fossil fuel, albeit sparingly. And above all, lean is the result of a design and construction process which itself is well-honed, focused on increasing value.

Lean is NOT scrawny or cheap. This is not about cutting corners, or sacrificing comfort. Indeed, lean can result in something quite luxurious.

Rich - The Western world has long equated wealth with excess. The Victorians of the late 1800’s had rooms for maids and separate rooms for public vs. private. We carry on this fine tradition with the formal dining rooms and living rooms in our McMansions, adding our own excesses of oversized great rooms, and tall ceilings which do nothing to improve comfort, but are designed for grandeur.

But now our world is faced with the reality of diminishing resources. Neither shame nor responsibility will have any impact as long as “downsizing” is equated with poverty. Is there another way to display wealth; is there an alternative which is both more environmentally responsible and equally luxurious?

According to experts on class, the well heeled “old money” choose quality and understated design in clothing and furnishings. Could it be the same for housing? Luxury might be described as the security of living in a strong, sturdy house which offers a haven from storms, built of quality materials which age gracefully. It can also be expressed in a level of comfort, with a stable, even temperature throughout the house, without the discomforts of periodic blasting hot air followed by a chill. Richness is expressed in a quiet interior, protected from the racket of the exterior world by solid insulation.

Sexy - While President Obama admitted that insulation may not be sexy, surely green building is. “Green” is the favorite buzzword in Hollywood, “de rigeur” for architects, and a marketing edge for manufacturers. Green taps into the pulse of a world which has been saturated with manufactured sameness, and is now craving hand-made (oh so much better than home-made), organic, and yes, simplicity. Minimalism is in, overconsumption is the “Biggest Loser.” Lean has always been sexy.

I predict that the new face of construction rising out of the recession will be lean, rich and sexy. The power will be with those who can make this dream affordable, realistic and sustainable. It is the hope for our industry, where craftsmanship is restored to our trade, where we take pride in building legacy structures, where our quality and comfort catches up to the rest of the world’s developed countries. This is not my crystal ball, nor a wild dream, but observations of early adopters, putting product out to market to test the waters, taking the pulse of the market.
Lean, rich, and sexy - what’s not to love?