Raised Heel Trusses - Raised heel roof trusses are made with an additional block to raise the heel height and accommodate higher levels of attic insulation. With a standard truss, the top chord rests on the bottom chord and allows almost no space for attic insulation after attic baffles have been installed. Depending on the roof pitch and the R-value of the attic, the first 2 - 3' of the attic perimeter is uninsulated or under insulated. With the 12 or 13" raised heel truss HFH uses, the reduction in attic insulation is negligible and the energy savings justifies the small additional cost of the block.
Radon Mitigation - Starting with our homes in Shadow Grass Park, we have been testing for radon and mitigating as necessary. This is not required by code, however we felt it was a good investment in our homeowners' health given that the EPA lists elevated radon levels as the leading cause of lung cancer after smoking.
The testing and mitigation process is fairly simple. After drywall is up and the house can be closed up for a couple of days, we test for radon. If radon levels are over 4 pCi/L, our contractor installs ubertough poly on the crawlspace floor, seals it to the wall and installs a fan and pipe to vent the gas to the exterior. The home is then retested to verify radon levels are acceptable and mitigation is successful. It’s a significant step towards improved indoor air quality and another way Habitat is building high performance homes.
Prison Partnership Cabinets - HFHSVV has been using cabinets manufactured thru HFH Colorado at Crowley County Correctional Facility east of Pueblo for several years. It’s a strong relationship that has served us, and the inmates who build the cabinets, well. HFHSVV only pays for materials, which allows us to get custom, well-built cabinets at builder grade cabinet prices. For Crowley County inmates, it allows them to build vocational skills that translate to a stable job upon release, giving them a better chance of succeeding in society after prison.
In addition, these cabinets are available at the ReStore for purchase by the public. If you're in the market for cabinets, swing by and take a look. ReStore hours, location, etc can be found at the Restore website.
Energy Ratings - 239 Sweet Valley had a professional energy rating done to assess its energy performance. The rater looks holistically at energy consumption of the home, testing duct leakage, duct leakage to the exterior and air infiltration. In addition, the mechanical equipment (furnace, water heater, energy recovery ventilator), appliances, and lighting--anything that uses energy is included in the calculation of total energy consumption. The rating also includes a rough inspection to check for thermal bypasses, quality of insulation installation, insulation levels etc. After both inspections are complete, a HERS score is assigned on a scale of 0 to 100, with 0 being a net zero home and 100 being a code built home. 239's score of 54 means that its three times more efficient than Energy Star and uses 46% less energy than a code home!
Wall on Grade - The Copper model uses a wall on grade foundation system to conserve resources, increase schedule efficiency and make it easier to pour a foundation with volunteers. Wall on grade is simply a typical foundation wall, but without the footer. Since our homes are smaller, we can use an 8 or 10" wall to support all the floor and roof loads, while still meeting min and max soil bearing pressures. Wall on grade takes a little more hand digging to get the forms level, but it saves a day of forming, a day of pouring and saves a little concrete over using a footer. Overall, it’s been a good move now that we're pouring our own foundations again.
Optimum Value Engineering - Since Shadow Grass Park, HFHSVV has been using Optimum Value Engineering (OVE) framing techniques. OVE is simply designing homes to get the most value out of the frame using 24" OC stack framing, headers sized for loads and exterior walls constructed in 2' increments and other techniques. In the Copper this plays out in several ways. First, the main exterior walls are 26', 24' and 28' instead of 24'5, 23'4 and 27'3. This reduces cost because each stud is fully utilized and there's less waste for sheet goods and siding. Second, 24" OC framing reduces framing lumber by 20% over 16" OC and increases the amount of insulation in the wall. Third, with headers sized for load we can use less lumber and more insulation above windows and doors. In fact, most of the gable windows and doors only have a flat header. All of this means lower cost to the homeowner, less material consumed and better energy performance.
Our Standard Home - Habitat's mission is to eliminate poverty housing worldwide and our affiliate accomplishes our share of the mission by building simple, decent affordable homes. In keeping with the mission, our standard home is a three bedroom, one and a half bath on a crawlspace with a single car garage. A ranch is typically around 1250 - 1325 sq ft, while the efficiencies of a two story allow us to build an 1150 sq ft home with approximately the same living space. This home will serve a family with two parents and up to three children. The scope creeps towards more elegant finishes, more square footage, bigger garages, etc. It is a constant pressure, but we balance each decision with our simple, decent, affordable mandate
Basement vs. Crawlspace - Habitat uses crawlspaces for construction, as they have proven to be the most economical and do the best job of fulfilling our mission of simple, decent, affordable housing. Occasionally, we'll get a question about our rationale and the numbers behind it. For a recent Architectural Review Committee request, I ran some rough numbers on basement vs. crawlspace costs and found a basement would be an additional $13000 over our crawlspaces. Although the additional space would be a nice benefit for the family, we simply couldn't justify this increase in cost and loss of volunteer opportunities.
Porch Posts - HFHSVV has built some mighty fine porch posts in the past--square bases with one square post, tapered bases with one square post, tapered bases with three posts and just plain tapered posts from top to bottom. While these looked good and matched the style of the house, they were very labor intensive and caused several schedule pinches.
To make life simple, we've been using 6x6 RealPosts for the last year or so. They're made from real wood, as the name implies, but they're made from four pieces of textured, primed lumber that are glued together lengthwise to form one hollow post. They look architecturally correct and eliminate the defects and warping associated with solid 6x6 posts.
Truss Bracing - In most cases, trusses require Continuous Lateral Bracing to perform to design. The truss webs are usually made from a low-grade lumber (#3 or utility), where the top and bottom chords are typically #1 or machine stress rated. CLB is used to reinforce the weaker webs against buckling under heavy snow and wind loads. These are commonplace and can be seen in most attics. However, Habitat uses higher-grade lumber for the webs, eliminating the need for CLB in most cases. This makes the trusses cost a little more, but saves volunteers from climbing around in the trusses, trying to get the bracing in the right place.
National Association of Home Builder's National Green Build Standard (NGBS) - The NAHB has created their own Green standard, similar to LEEDS or other green ratings, with a focus on sustainability, durability, water and energy conservation and indoor air quality. The work and features we put into 303 Sweet Valley resulted in a Silver Rating, independently verified by a third party rater--while still maintaining affordability. You can see more details about the NGBS at www.nahbgreen.org. Thanks for your help towards this milestone!
Mudsill and Top Plate Air Sealing - We've tried several methods to seal the SIS board to the mudsill and top plate, with limited success. Gaskets and mastic were leaky and hard to apply, so on 304 Sweet Valley we used 4" window flashing, which was at least easier to apply and looks like it will seal well.
For the top plates, half the flashing goes on the plate itself and the other half goes over the SIS board. The flashing sticks well to both and is pretty durable when we're rolling trusses. For the mudsill, about two inches of flashing sticks to the SIS board and the remaining laps over the mudsill and onto the foundation. It’s critical that the flashing be tight to the SIS board so it doesn't trap water, but that's pretty easy to manage.
The blower door has the final word, but it looks like it’s really going to work.
Recycling - To be kinder to the environment and our construction budget, HFH recycles as much construction waste as practical, including untreated, unpainted lumber and OSB; any untreated wood products; #1-7 plastics; aluminum cans; metal; cardboard and paper. All of the recycling is free, though it has to be delivered to various places. But it costs $50 per empty on the bin, so it makes environmental AND economic sense.
Easier Entries - Accessible houses are becoming more mainstream in new construction as the population ages and stays in their home later in life. There are varying degrees and components of accessibility, but one of the primary pieces is an accessible entry. Ideally, the house has at least one entry that has no steps, but it’s not practical in subdivisions like Mill Village with small lots and tricky grading requirements. Starting with 303, we've tried to make the house more accessible by making the front entrance from long landings instead of the traditional three steps, 36" landing, three steps model. This makes it easier to get from the street to the sidewalk with crutches, a walker, etc. but avoids the complexity, cost and potential ugliness of a typical ramp.
Pump Jacks vs. Scaffolding - When we started building two story houses, one of the primary concerns was putting up siding quickly and safely. There are really only two viable options: pump jacks or scaffolding and we selected scaffolding for several reasons. Scaffolding allows almost an unlimited number of volunteers on it at once, the setup is relatively safe and easy compared to pump jacks, there's more room to work and it feels a lot more secure to the average volunteer.
Scaffolding does have some trades off, though: it’s slower to assemble and disassemble, takes more space in the trailer and can't be used against tight fence lines. These are among the reasons that most siding contractors use pump jacks.
Sprinkler Systems - Starting in Shadow Grass Park, we put in sprinkler systems--primarily because the HOA required it. Starting with Mill Village, we've been putting in sprinkler systems because we thought it had enough benefit to offset the costs. First, we're trying to be more water conscience. Landscape water makes up at least 50% of total water usage for the whole year and we felt like a hose was a huge water waster. Since we are using low demand fixtures on the inside, we felt like we should be more responsible with water on the outside. Second, it means the grass and plants stay green and alive during the summer. This keeps the neighbors happier and helps the homeowner fit in better. Again, this is possible with the hose, but a lot less likely.
Standard House - Our standard house is a three bedroom, 1-1/2 bath. Both the Durango (ranch currently under construction in Dacono) and the Copper (two story in Mill Village) are about 1300 gross sq ft, with a half bathroom and mechanical equipment on the first floor, making it easier (theoretically, if any homeowners remember) to perform routine maintenance. The half bath is meant to support the living area and the compartmentalized main bath is for the residents. We try and make the floor plan open so it seems a little bigger and has more useable space and less hallway space.
Nail Guns - HFH Affiliates have varying opinions on nail gun use on the site. Some don't allow guns at all, some significantly limit their use and some use them like a professional builder would. While being mindful of safety, we fall in the third category for several reasons, primarily speed and the need for a gun to make advanced construction materials work.
For example, the rimboard for our floor isn't practical for hand drives, the SIS board sheathing requires a gun and siding over foam doesn't install well without a gun. Beyond practicality, there's a production component-- we want to get the house built quickly and hand drives everywhere take a lot more time. With those factors in mind, there are still times we don't use guns. Volunteers under 18 can't use guns because of insurance restrictions. When we have big groups, we don't want them to watch one guy nailing when they could all be busy. And, sometimes it’s a little more satisfying to nail walls together with your hammer. Above all, watch for safety when we do pull the guns out.
Tankless Water Heaters - We've used tankless heaters for the last few years for several reasons. They're sealed combustion so there aren't any concerns about back drafting, indoors air quality, combustion air, etc. They're compact and we don't have to give up floor space for a water heater or put a low-boy in the crawlspace. They're also 0.82 - 0.96 energy factor, compared to a tanked model of about 0.65. I don't think they're for everyone; especially retrofit scenarios where the gas pressure and/or line would need to be upgraded. They also cost more than a tanked unit, but aren't too much more than a sealed combustion tanked once you figure in the flue in new construction. The only complaints I've heard from homeowners is that the water isn't hot enough, but someone turning up the controller too high typically causes that.
Square Floors - Lately, we've been getting precut floors from the lumberyard. This is good for us on two accounts. First, we don't need a saw to build the floor, i.e. the floor goes on quicker. Second, and more important, it allows us to get the floor square.
To do this, we assemble the floor without nailing anything but the back wall to a chalk line on the mudsill. Then, since we know the floor is the right dimension we measure diagonals and move the floor until its square. In the best case, everything lines up with the mudsills. But, if we're off a 1/2" we don't sweat it too much since the floor is square. This gets repeated for the second floor so we've got an easier time putting trusses on from there.
Townhomes - 1713 and 1717 Spruce will be our affiliates first attached home. Its like the homes we built at Mill Village--it just shares a common wall instead of a 5' side yard. It also allows us to increase density and reduces construction costs. Each unit will be individually owned and doesn't require an HOA for maintenance. Since it’s a front load, the layout downstairs is slightly different, but otherwise the same as the Coppers we've been building with three bedrooms, 1-1/2 bath, 1300 sq ft, etc. We'll have to put up a fireproof wall, but otherwise the construction details will be the same, too.
Stepped Foundation on Townhome - As you may have noticed, the site for the townhome runs downhill to the south quite a bit, enough that the grading along the front of the house is 5' higher than the grade at the rear. Using a foundation at one height would require 6' forms (which we don't own) and a footer (which we’re adverse to pouring due to time and cost). To solve this, we used a stepped foundation and a pony wall. The top of wall is 2' higher on the front part of the foundation, which makes the grading work. To get the floor back to the same level, we'll use a wood framed pony wall. This is similar to what you see on a walkout basement.
Hangered Floor Joists - To make the grading work better on the townhome, we're using hangered joists, which makes the house 12" shorter. To use a hanger, mark the plate on layout, but make a mark for both sides of the joist. Attached a snap-in (as opposed to nail-in), top mount (as opposed to face mount) hanger using two Teco nails making sure that its a little open at the top so its easy to get the joist in. Also, make sure the sill doesn't hang more than 1/4" over the wall or there's a risk the hanger will split the sill. There should also be a shim on the hanger side of the sill or it will roll. After the hangers are in on both sides, drop the joist in and move to the next one.
Ganged Trusses - For 1721, we couldn't get the crane until about 2 pm and given that its dark by 515 or so, I wanted to make sure we could get the whole lift done. So, in the interest of time, we ganged together trusses in sets of four on the deck of the townhome. We plumbed the first and tied the other three together with spacers and diagonal bracing. To make setting the gables easier, we set one gang first so there was a nice place to stand when wiggling the gables around.
As it turned out, setting ganged trusses worked great and even with some rough weather we got the crane out in record time. Going forward, the crane operator suggested we do batches of six and only tie them together at the peak. That would mean we'd only need three lifts for commons and four lifts for gables--lots of time saved!
Shaft Walls - For the townhome, we'll be installing a shaft wall to separate the two units for fire code and noise purposes. The wall, made from two layers of 1" rock, floats in the 4" gap between the units and is connected to the framing with aluminum clips. In the case of fire, the clips on the burning side melt, the framing falls away and the shaft wall is left attached to the non-burned side. For noise, it creates an airspace between the two units that virtually eliminates sound transmission.
USG has a pretty decent guide for more info and pictures if you're interested, www.usg.com/rc/system-catalogs/usg-area-separation-walls-catalog-en-SA925.pdf
Multilap Siding - As you've probably noticed, we use multilap (AKA cottage lap) siding for most of the building, with lap siding as an accent in a few places. Multilap siding is significantly more costly than standard hardboard lap sidings, though we think the benefits outweigh the additional costs.
The overarching reason is that it’s a lot more volunteer friendly. To get multilap started, we only need to snap one chalk line around the house instead of lines for each course like lap siding. Although it can be done incorrectly, the ship lap generally keeps the siding aligned the rest of the way up. Since trim boards go on over the top, we can make ugly cuts at the corners and around openings. This also allows us to start siding with big groups sooner as we don't have to have all the trim up first. We can also use aligned joints and cover them with a batten strip instead of fooling with band-aids to cover the gaps.
Despite the negatives of cost and 16" OC framing required by the siding manufacturer, we think it’s a good deal
Improved Communications - Over the summer, with the help of several volunteers, we've improved our construction web page substantially. It now contains all of our quick guides, blueprints for the current homes, primers on tool safety and a list of tasks for upcoming work days. The objective of these new features is to make construction faster and more efficient and enable new volunteers to be more engaged in solving affordable housing issues in their community.
The quick guides are designed to be a two page basic overview on: what tools and materials are needed, safety considerations, team roles, common mistakes mad finally how to do the job. We'd like to use these to help our leads review what needs to be done ahead of time and review what needs to done with their crews to make construction faster and more efficient. Hopefully, you'll find them helpful when you're on site.
If you've got a few minutes before you come to work, take a look at the blueprints to see what we're building is supposed to look like. We tend to make at least a few mistakes per house that could have been avoided if we'd spent a little more time with the plans.
The workweek PDF contains a detailed list of work for the next several days. I'm hoping to update it Tuesdays and Thursdays to give people a better idea of what we're working on. At some point soon, we'll post the entire schedule so people can see how we're doing vs. baseline. Last, now that there's a solid list of the volunteer tasks available on the web, I'll try sending one email a month instead of two.