Farming Magazine - May, 2013

FEATURES

Construction by the Book (or Not)

By Martin Harris Jr.


Photo by AcrylicArtist/morguefile.com.

Agricultural construction isn't what it was in your grandparents' day. Today there are construction techniques and off-the-shelf components that were unavailable a few years ago; new design problems the experts have caught up with; and a range of new mechanical-electrical items that address some of the old problems.

Building codes

For decades, there has been a range of mostly regional building codes - BOCA in the North and SBC in the South, for example - but these are now being replaced by a series of relatively new International Building Codes (IBC) similarly adopted at state level. They now govern public buildings as well as private ones (including agricultural buildings) that used to be exempt. There are only a handful of states, such as Arizona, that specifically exclude ag construction from IBC enforcement.

Some states, like Vermont, have preceded the new IBC residential code with state-level energy efficiency requirements that come, in part, from such industry standards as ASHRAE 90.1. There are also standards like NFPA 13 (from the National Fire Protection Association), which controls fire suppression system design for buildings that are required by both the old codes and the new IBC to be fitted with sprinkler systems.

You need to know which codes your state (and in a few cases local government) has adopted, and follow them for three reasons.

One goes back to the so-called "10-acre loophole," whereby, with enough land, you could build any on-site effluent disposal system you wanted, as long as no adverse results crossed your property line. The underlying reasoning: no public nuisance, no public control. However, today, if you're on public water, public sewer (or even if you're not), regulated utility and so on, you could adversely affect the public and therefore are subject to regulations.

The second reason goes to government's increased interest in building permit fees. And the third goes to today's enhanced litigation climate: Evidence of code compliance is your best first defense against personal injury lawsuits from vendors, customers or even visitors to your commercial buildings. With a 42-inch handrail guard you're code-compliant; with a 41-inch guard, you're not.



Photo by Hans/pixabay.com.

Managing fire risk

Fire has been a hazard for agriculture for as long as hay has been stored for livestock, with both often in the same structure. A few years back, round-bale enthusiasts predicted the end of that thousand-year tradition, but because of recent trends in small-scale farming and hobbies, the hand-managed square bale hasn't gone away as envisioned. Neither have haymow fire risks.

Until recently you couldn't find an electrical smoke detector or rate-of-rise detector labeled for installation in a cold space like a haymow, but now you can. Manufacturers in the mechanized air handling sector have ordered them for duct protection, and engineers have responded. The industry now offers detectors specifically labeled for use in low ambient temperatures, and while they're not specifically labeled for haymows, there are no code violations involved if you install them on your own. With the magic of electric wiring, the danger signal can be routed to an alarm signal anywhere on the farm. Also, it could be set up to trigger your own fire suppression system, identical in principle (but not in NFPA-13-mandated detail) to the fire suppression installation required in the public building sector.

As with detectors, the choices for fire suppression systems are better than they once were - not just your grandparents' rigid, threaded pipe and fittings anymore. The industry offers a range of plastic fittings and pipe, both rigid and flexible, designed for a range of cut-and-paste and cut-and-press-fit connection systems. The range of sprinkler heads provides either conventional, "deluge," or mist water application when the supply controls and/or valves are triggered by a smoke or heat signal.

If you don't want to use antifreeze in your cold environment's supply lines (the NFPA has recently banned both ethylene glycol and propylene glycol for code-controlled residential applications), you can use an electrically motorized valve to admit clean water from your warm area's supply into the cold area's distribution piping when triggered by a detector signal. Your system isn't code-controlled, but if it's connected to your domestic water supply, a backflow preventer is required. You don't have to comply with the minimum water supply requirements in NFPA 13, but you should size your system for at least a few of your sprinkler heads to discharge simultaneously - for example, in a single hot spot in your haymow storage.

What about wind load?

Now for the wind load question related to open-front livestock (and some ag retail) construction: How do you calculate the total uplift loads when some derive from conventional roof or wall exterior negative pressure and some derive from similar building interior positive pressures? A clear discussion of this subject can be found in the article "Wind Safety of the Building Envelope" on the Whole Building Design Guide website (www.wbdg.org). It specifically calls for calculating external and internal positive and negative pressures when designing against lateral wind loads and uplifts. Some in the industry don't, and the codes are unclear. Be advised.

Product improvements

  • The building components industry continues to introduce remarkable new products and innovations. Even a brief list should include the following:
  • New concrete pier systems for pole construction, with improved steel connectors to the wood pole far enough above slab level that the old concerns over physical and organic damage are minimized.
  • The expanded availability of engineered lumber for framing and trusses, and similarly engineered composite lumber for finish and trim.
  • Greater awareness of metal fastener and connector characteristics with regard to two critical areas - resistance to treated lumber chemicals and resistance to withdrawal loads.
  • A variety of "indoor" items ranging from damage-resistant insulated panels to more sophisticated air handling equipment, both powered and fixed, to improve indoor temps and minimize the usual problems with air quality, moisture and vapor in ag buildings.

Potential geothermal application

There's one sector of energy management for buildings that is no longer cutting-edge, but still isn't widely familiar or available either: geothermal.

This is mostly due to cost - low-tech/low-cost consumer applications haven't surfaced yet. An easy application the industry has overlooked is based on the annual soil temperature curve, specifically the lower-than-ambient temps available at depths from 2 to 4 feet (depending on your site latitude) while summer temps are 40 or more degrees higher.

For example, in New England, groundwater and soil year-round temps average in the mid-40s, even in those months when it's now standard for living and business space to be air-conditioned to near 70 degrees when air temps are 80 degrees or above. Conventional compressor-evaporator AC uses that solar-overheated air for cooling purposes, an electric-power-intensive process compared to the near-free availability of ground-cooled water and air just a few feet below grade.

Across the country, a few (mostly homeowners) have used private well water for fan-powered interior cooling (a small fan blowing across a copper coil array will work), but even fewer have used the cool soil temps directly. This is done by using buried 4-inch plastic piping with a small blower to chill warm air and introduce enough of it into occupied space to get temps in the 70s rather than the 90s. Yes, there are some moisture and mold hazards to defeat, but it's a way to condition summer air that offers a low cost and a high coefficient of performance, and as long as you have the land for pipe burial, it's very easy to set up. Just a thought.

The author is an architect and former farmer.