Saturday, July 4, 2009

Home plans update (one of many)...

(Brendan)

Again, it's impossible to adequately follow the previous post, so this post will seem kind of silly. Nonetheless, we are excited about closing on our house and getting started on our new house, and I thought I'd do some posts on things that have changed since our set of bid plans. For the best background for this post, I'd recommend re-looking at where we were at the end of the bidding process (including known cost-cutting measures at the time).

This post specifically regards the elimination of the basement that we had originally planned, and our new plans for the home's foundation. Eliminating the basement was certainly done in order to save on cost, but the decision was made very easy when, in further conversations with the city of Ham Lake, MN, we were informed that our original plan would not be allowed since the depth of the basement was below the water-saturated soil level (which, due to the wetland nature of the Ham Lake area and our particular lot, is only a couple feet below the ground level). Never mind that this detail should have been given to us a long time ago on our site plan (and that it was written on a "livability plan" document that the city had, but we were never given), in the end all that matters is that elimination of the basement needed to happen. Due to our architectural sensitivities with this home, we also were not going to go with some sort of large grading effort to create an artificial hill for the home site in order to have a walkout basement (this would also be necessary even to create a simple crawl space). Actually, the neighbors to the South of our lot did that, and it looks a little silly. So the best option for us was to go with a simple slab-on-grade foundation (basically a solid concrete foundation, with frost-footings).

Switching to slab-on-grade is no simple deal when the house was completely designed with a basement in mind. Here's a list of just a few of the challenges this creates:
  • Where do we create above-ground storage space?
  • All the mechanical systems were going to be in the basement. Where will these go?
  • Air ducts were being run through the basement ceiling, how will these be re-arranged?
  • It's Minnesota. The first-level floors will be freezing cold in the winter with a slab foundation, won't they?
I'll address these challenges in future posts. The final bullet point I'll address here. We decided, with our general contractor's advice, to go with a hydronic radiant heating system on the first level. This will cost us moderately extra, but not too bad (4 figures, total, for the rough-in of the tubing and the mechanical services). Coupled with the large savings of not having a basement, it's still a big net cost savings. And it will be almost a necessity in the winter simply for livability and enjoyment of the home. No one wants to walk around on freezing cold wood floors. With radiant heat, floors will be toasty warm in the winter and will be a pleasure to walk on barefoot.

Here's how it works. During creation of the slab foundation, tubing is weaved and secured to a grid of rebar (or other support system), ensuring coverage of all areas of the floor. Concrete is then poured over the tubing, embedding it in the slab. The tubing will carry warm water through the concrete floor, warming the floor and eventually heating all of the rooms themselves as the heat radiates upward. It's a very clean, efficient, non-allergenic, and comfortable way to heat a home. The upstairs will still have air services for heating, but hopefully that mode of heating will be infrequent as the lower-level heat will also contribute, indirectly, to heating the second-level (especially with our highly insulated SIP's home construction).


Above: A section view of a hydronic radiant heating system installed in a concrete slab foundation. The water-carrying tubing is embedded within the concrete and is insulated from the bottom to prevent heat being transmitted to the ground. (Okay, the guy with the blue socks is annoying, but the time investment needed to photoshop him out just isn't worth it ;-)

Below: Examples of hydronic radiant heating being installed in new construction.


The case for radiant heating over forced air: with forced air we heat our ceilings (wasted heat) and the floor is the coolest part of the room; with radiant, it's the opposite. Because of the higher efficiency of radiant heat, it also costs less to heat the home. Why doesn't everyone do radiant then? Simply because of the higher up front costs (though you can get your money back over time with reduced heating bills).
One final note, this works ideally with concrete floors, and also does work particularly well with engineered wood floors. It can work with hardwood floors too, but you have to be careful which wood species you go with (the harder, the better). The issue is expansion and contraction of the wood. Engineered wood floors are multilayer constructions that don't expand and contract much, and that's the type of wood flooring we choose for the house anyway.

9 comments:

Sarah said...

So where do you go in severe weather?

Brendan Koop said...

We will have a windowless storage room that we can go to (I'll talk about that in a future post). Also, since we are using structural insulated panel (SIP) construction, which is 2.5 times stronger than standard stick-framed homes, the home will be substantially more resistant to damage.

John Curran said...

What are these storm shelters of which you speak? Tornadoes?

Nothing like that in NJ, not since the fallout shelters during the cold war.

Very interesting update--- will be following along...

Brendan Koop said...

Let me illustrate for you :-)

Here is a good summary of the May, 2008 tornado in Hugo, MN:

Link

Hugo is 15 miles East of Ham Lake.

I would say we typically have 3-4 tornado warnings per summer in the Twin Cities (i.e. the sirens go off and we have to go down to the basement or some safe area to sit as a family until the warning is over) We have around one devastating tornado per year in mid Minnesota, with lots of damage.

If you look at the utter devastation of the Hugo tornado last year, more than a few articles have been written pointing out that houses should not just completely disintegrate like that, even in the direct path of a tornado. From an engineering standpoint, home construction (particularly the stick frame variety) has gotten so quick/cheap in the past few decades that this type of devastation isn't surprising. The other factor that has been identified is the size and strength of garage doors. Large garages are bad news for tornadoes because the garage door gets blown inward and then the garage acts as a big "catch" for the tornado and is the initiation point for the house being ripped off its foundation. Our home will have two single car garage doors, which are much stronger in this scenario.

At any rate, even a basement is not a lot of comfort or protection with devastation like this. The key is building a strong, well-constructed house. In our case, windows may be damaged, trees may blow over, the roof may loose shingles, but the house isn't going anywhere. Due to the SIP's it is basically one continuous I-beam envelope, extremely strong.

Molly Koop said...

It's interesting that SO many Minnesotans have asked this very question about storm shelters. I grew up with a weather ban radio in my house (but then, my dad was a retired police officer and loved to listen for storm warnings all over the state). We even have test sirens every Wednesday at 1pm during storm season and tornado drills in schools. Now that I'm a mom, I've noticed that most storms happen just after I've gotten all the kids into the tub or in bed. Murphy's Law, I guess. Praying for a safe storm season for all us mid-westerners.

Jenny Clarke said...

The best is when all the kids are in the tub, the electricity goes out and the tornado sirens begin...

Michelle said...

Hi Brendan and Molly - I heard about your blog from Brian and Sarah and have read posts here and there along the way - fascinating! Anyways, I wanted to comment on this post because my husband Jim just graduated with an HVAC degree and is all about trying to find energy efficient ways to do heating/cooling. We just bought a house which was in the middle of a big remodel, so he jumped on the opportunity to put in-floor heating in as many parts of the house as possible (while still keeping the original structure intact). My question is, why not go with geothermal heating/cooling for your place? A couple years ago, Jim and I talked about building a house because of the potential for energy savings and he said that, if you're building a home you should without a doubt take advantage of the chance to put in a geothermal system because ultimately it is the most efficient way to heat and cool a house. Or would this not be possible for you because of the high water table level on your property? Just a thought...

Brendan Koop said...

Michelle! You are stealing our thunder! :-)

Suffice it to say, we are looking at it heavily and are waiting to confirm it before we do a post on geothermal.

Stay tuned for a future post...

Michelle said...

So glad that you're looking into it!! Sorry to steal your thunder:) I'll look for that post.