Panelized

Panelization gives conventional builders a huge edge over their stick-building competitors by allowing a house to go from the foundation to being dried-in in 2-3 days or sometimes less, depending on exactly how the panelization is done. This process often takes several weeks with conventional stick framing. Exterior and interior finish work is performed in the usual manner with most systems.

Wood-frame panelization began with stick-framing; the only difference was that the walls, floors, and roofs were stick-framed in the factory rather than in the field. Stick-Frame Panelization (SFP) is still very popular today because stick-framed walls are very familiar not only to the builders, but to their customers.

The late 1970’s saw the rise of re-conceived panelized construction. The Structural Insulated Panel system, or SIP, for short, was composed of two layers of plywood glued to a core of foam insulation. SIP panels are exceptionally strong and stiff even though they contain no rafters, joists, or studs, and typically have insulating values far in excess of a comparably-sized stick-framed wall or roof that is insulated with fiberglass batts.

Recently, SIP panels themselves have been re-thought, except this time, it is a refinement rather than a reinvention. Fiber-reinforced cementitious siding has been used for years as the exterior cladding of buildings. Some clever inventor realized that not only was the material very strong (it is, after all, made mostly of concrete,) but it is also rot- and termite-proof. So they replaced the plywood skin of SIP panels with Fiber-Reinforced Cementitious sheets, creating a wall panel (the FRC-SIP) that can be dunked in water and will dry out just fine. Katrina Cottage II with built with these panels.

Now, inventors around the world are reinventing panelized construction at such a pace that it is hard to keep up with all the innovations. Some use foam-and-steel panels that are sprayed with concrete to any thickness desired, creating a hardened exterior that can be stuccoed. Because it is sprayed on both sides with quick-drying, gunned-on concrete (gunite,) the foam is encased forever in the center of the wall, insulating the heavy thermal mass of the interior concrete layer. These are generically known as foam sandwich systems (FSS.)

It should be noted that most of the panel systems involving concrete cannot be used on modular or manufactured housing. If not, then why include these systems on a site dedicated to Katrina Cottages, which from the beginning were meant to be deliverable by all major construction methods including manufactured and modular housing? This is because it is feasible to take a Katrina Cottage design which could be manufactured or modularized and simply replace the exterior frame wall with a concrete-based panel system and build it on-site.

Some of the new foam-and-concrete systems reverse the arrangement, building walls quickly of very large foam blocks that create a permanent form into which to pour concrete that creates the structure of the wall. These Insulated Concrete Form, or ICF, Systems are technically not panelized systems because they do not construct walls of full-length panels, but they install almost as quickly as the panelized systems.

Two other distinctions between concrete-in-the-middle (ICF) and concrete-on-the-edges (FSS) systems are: 1) FSS walls are much more resistant to mechanical damage such as being struck by a line drive or by a rock thrown out of a mower, while 2) ICF walls create a straighter finished surface because the stucco installer is finishing over factory-milled foam rather than field-applied gunite. So if you’re looking for a very crisp wall, it’s easier to do with ICF, but if you’re looking for a very relaxed, organic-looking wall that looks as if it may be stuccoed over a natural stone structure, then that comes naturally to FSS.

The Aerated Autoclaved Concrete (AAC) blocks are similar in size to the ICF blocks, except they are made of a concrete mix that is put into an oven (autoclave) and expands dramatically when it is fired, creating air bubbles throughout the block (aerated) that create serious insulation value. AAC blocks are solid; even though there are no cavities like you find in regular concrete blocks, they are both lighter and longer than ordinary block because of the aeration of the concrete. They can be cut with regular hand tools, and need no additional insulation. Some AAC companies now build wall panes as well as blocks, so you can get panels with wall and door openings blocked out shipped to your site.

There undoubtedly will be new panelized systems developed in the near future; please let us know if you are aware of some. In particular, we want to know about systems that are able to be submerged every 25-30 years and dry out without damage.

Panel Systems

Panelized-Housing-cover

This Panelized Housing system was developed by the Center for Applied Transect Studies in Miami by Andrés Duany and Matt Lambert. It includes both a panelization system, a set of cottage plans that work with the system, and an architectural code that allows for customization of the character within appropriate ranges.

The following are companies that produce panelized systems in the categories above.

SFP - Stick-Framed Panels

Manufacturing plants across the country make SFP panels; they are so numerous that it is not feasible to list them all here. Builders should know the best local SFP fabricators.

SIP - Structural Insulated Panel

SIP manufacturing plants are almost as numerous, and will not be listed here, either. Rather, check with the Structural Insulated Panel Association website, which lists all of the manufacturers and builders in your area.

FRC-SIP - Fiber-Reinforced Concrete Structural Insulated Panel

One of the pioneers of the FRC-SIP is Homefront, which is the company that supplied the panels for Katrina Cottage II, Katrina Cottage V, and Katrina Cottage VI.

FSS - Foam Sandwich System

FSS has been under development for several years, but early systems had the troublesome little detail of panels that must be cut to fit on the jobsite, creating veritable snowstorms of styrofoam debris for as long as houses are being framed. Needless to say, the required cleanup was an issue, as was the fact that the sales team was always battling the repeated question of “are you building this place out of drinking cups?” Shortly after Katrina, Green Sandwich Technologies solved the problem with several improvements, including manufacturing all of the panels off-site so that they need only be assembled very quickly onsite before being shot with gunite. They have unfortunately gone out of business in the years since, but another manufacturer should pick up where they left off because the system held great promise on several counts.

ICF - Insulated Concrete Forms

As with SFP and SIP systems, there are numerous ICF manufacturers. The industry trade organization is the Insulating Concrete Form Association. One word of caution: in a hurricane zone, be careful to ensure that the finish applied to the surface is strong enough to resist impact from wind-borne debris.

AAC - Autoclaved Aerated Concrete

Until a few years ago, there were only two principal AAC manufacturers in the USA. Today, there are several. Their trade organization is the Autoclaved Aerated Concrete Products Association. Originally, AAC manufacturers in the US produced only AAC blocks, meant to be laid similar to concrete blocks. Now, however, some have expanded to custom-built wall panels, significantly speeding construction.

© New Urban Guild 2017