New house questions

[luscsmith]

Hello to all, I am planning on building a house in Alabama and have a few questions that I think can be answered by this multi-talanted group.
First should the ceiling or roof deck be insulated? My understanding is that you insulate the roof deck so that the HVAC ducts don't transfer the heat as much. Would it not be better to insulate the ceiling and super insulate the duct work?
The second question is what are the pros and cons of a slab built verses a crawl space?

I know I will get some brillant answers from brillant people.

Thanks, Scott

 

[Cat_Driver]

My advise is always OVER insulate it will save you in the long run.
Slab better than crawl space because termites do not like cement.

 

[chucko]

most times the ceiling is insulated or you will be heating/cooling the attic

 

[luscsmith]

That is my understanding that it is recomended to heat and cool the attic, witch inturn saves energy loss from the duct work. It really doesn't seem correct to do it that way that is why I thought it would be better to just super insulate the ducts.

Scott

 

[brin]

Hello to all, I am planning on building a house in Alabama and have a few questions that I think can be answered by this multi-talanted group.
First should the ceiling or roof deck be insulated? My understanding is that you insulate the roof deck so that the HVAC ducts don't transfer the heat as much. Would it not be better to insulate the ceiling and super insulate the duct work?
The second question is what are the pro and cons of a slab built verses a crawl space?

I know I will get some brillant answers from brillant people.

Thanks, Scott

Remember with a slab all of your pipes are encased in concrete and if you ever have a problem just picture breaking up concrete to fix a broken pipe or a connection that came lose. It has been my experience homes with crawl spaces always have a higher resale value and you have wires and pipes available for inspection and service. You can and should have a termite treatment and contract whether on a slab or crawl space ..so I would not go slab to avoid termites..there are plenty of houses with slabs that end up with termites as well.

 

[Kays Supply]

In a crawl space house the duct work is in the crawl space. The cold air return is the only duct in the attic. In my part of the country the attic is almost outside temperature. The ceiling is super insulated. The cold air return is insulated. I built a pan and super insulated the cold air return in my house with the same blown in isulation as the rest of the attic.

Slabs are usually cheaper than a crawl. The contour of the land usually is a big factor in deciding crawl or slab. If flat it is much cheaper to go slab. If on a slope a crawl is usually cheaper than all the fill. I plumb both. The slab is quicker. So far with modern plumbing done by a professional, troubles under the slab aren't much of an issue. Changing your mind midstream is. I am prepairing to rough in a basement slab that the owner has changed the plan 3 times since we started.

 

[Western]

Going with a slab may give you more flooring options now and in the future, say if you decide on granite or similar flooring, you will want a good stout base to handle the added weight. Also it is allot easier to tile a concrete floor and maintain it with a slab, say in a bathc ect tra..

just a thought.

 

[woodchuckie]

I've never seen or heard of insulating an attic. We spend lots of money to see that we have flow thru ventilation in our attics. Keeps moisture buildup out and keeps the attic from becoming super heated in the summer. With the ridge vents, gable vents , soffit vents and even gable fans the attic isn't too much hotter then the outside air. The duct work in the attic can be the space above a lowered hallway ceiling which is made of formed insulation and the normal attic insulation is blown in on top of it. The rooms not reached by the hallway have flexible insulated duct work which can be covered by the attic insulation also. I would never put any of the heating or cooling parts in the attic. It will freeze. The heating and cooling can go inside in a closet.
I have a slab and have had no problems in 30 years. I wouldn't use copper with a high acid water supply in a slab. It won't last 20 years. A crawl space would be nice for the possible additional storage and other things you could do. They say you can't put a hardwood floor on a slab without a moisture test and putting plywood on it.
Are you just now moving to Alabama or.... Roll Tide.

 

[beenthere]

Being that global warming is coming (wink), you can skip the insulation.

However, given that you have just been through a cold spell, and that air conditioning to keep cool is more popular, doing the insulation seems smart and prudent. Seems it is an investment that will keep money in your pocket, as well as make the home more valuable if you need to put it on the market.

Regardless, there still needs to be the proper ventilation to vent the area above (or outside of) the insulation.

 

[20 20]

Insulation is like gold in a house. Up here we use as much as possible to keep in the warm. Down south I have been told use as much as possible to keep in the cool. So plan on over insulating you won't be sorry.

As far as slabs go, IMO I'd run in the other direction, I have seen many slabs that have failed over time, shifting cracking etc... Of course if your plumbing is in the slab then quess what happens when it does shift{IMO it will}. 1 example; Friend of mine had used a slab, when it shifted it plugged his septic. When they flushed the toilet it backed up into the house, cost was more then just releveling the house. I also have a few other stories of folks with slabs, and not just from the northern cold states. IMO opinion piers are your best bet, the ones I have done and worked on/with have had allmost zero issues{zero if done correct}.

 

[dave1949]

Insulation is like gold in a house. Up here we use as much as possible to keep in the warm. Down south I have been told use as much as possible to keep in the cool. So plan on over insulating you won't be sorry.

As far as slabs go, IMO I'd run in the other direction, I have seen many slabs that have failed over time, shifting cracking etc... Of course if your plumbing is in the slab then quess what happens when it does shift{IMO it will}. 1 example; Friend of mine had used a slab, when it shifted it plugged his septic. When they flushed the toilet it backed up into the house, cost was more then just releveling the house. I also have a few other stories of folks with slabs, and not just from the northern cold states. IMO opinion piers are your best bet, the ones I have done and worked on/with have had allmost zero issues{zero if done correct}.

No doubt about that. All slab problems tend to be big problems. What's up with basements in Alabama? Too many humidy problems? Drainage?
Dave.

 

[woodchuckie]

There are lots of basements and unless it's a hole with four sides the moisture isn't a problem with proper landscaping.

Just an afterthought, In the late 40's and early 50's the walls in new houses weren't insulated. They did have a few inches of insulation in the attic.

 

[dave1949]

There are lots of basements and unless it's a hole with four sides the moisture isn't a problem with proper landscaping.

Just an afterthought, In the late 40's and early 50's the walls in new houses weren't insulated. They did have a few inches of insulation in the attic.

The additional construction cost, especially up north where a 4' frost wall is needed, for a full basement compared to a crawl space is minimal. A basement can be inexpensive space by comparison. I guess down south you aren't putting in 4' frost walls and that would change the math considerably.

For access to plumbing, electric, ductwork, etc. a basement is hard to beat. Crawlspaces have too many spiders
Dave.

 

[eepete]

My house in North Carolina is insulated with the spray in foam. The entire house, including the attic spaces, is interior space. On a 103 degree day, the attic temperature was 85 degrees. I have ducts in the attic space, but all equipment is in the basement. In this neck of the woods, if you insulate the entire house you must have a metal roof. If you do shingles, then the attics space must be open and vented. Our old house was that way, and on a 100 degree days the attic temperature was about 135 degrees.

I agree with the "insulation is gold" approach. Payback on the foam insulation in 6" exterior walls was about 8 years. So you don't see this much in spec houses. Re-doing or changing insulation is as impractical and expensive as moving a wall once the place is built, so do it right the 1st time.

We have a basement, but we are built into a hill. This means the footer drains actually work. Problems with basements here are when people put a hole with four walls in the clay soil and then wonder why it fills with water.

Pete

 

[dave1949]

My house in North Carolina is insulated with the spray in foam. The entire house, including the attic spaces, is interior space. On a 103 degree day, the attic temperature was 85 degrees. I have ducts in the attic space, but all equipment is in the basement. In this neck of the woods, if you insulate the entire house you must have a metal roof. If you do shingles, then the attics space must be open and vented. Our old house was that way, and on a 100 degree days the attic temperature was about 135 degrees.

I agree with the "insulation is gold" approach. Payback on the foam insulation in 6" exterior walls was about 8 years. So you don't see this much in spec houses. Re-doing or changing insulation is as impractical and expensive as moving a wall once the place is built, so do it right the 1st time.

We have a basement, but we are built into a hill. This means the footer drains actually work. Problems with basements here are when people put a hole with four walls in the clay soil and then wonder why it fills with water.

Pete

I have seen pics and articles on insulated attics like you have. Never heard from anyone who owned them. Good to know it works out.

In a similar way, I have seen articles promoting incorporating a crawlspace into the house environment. Good vapor barrier on the ground, but insulated walls and no vents. Seeing any of that down your way?

Right on with the basements, there are no good basements without good drainage. They sure are useful if they are dry.
Dave.

 

[dmccarty]

I prefer slabs. Our dream house we built has a colored concrete slab. The slab is our finished floor. From grade to the floor is about 12 inches on the up slope side of the house. The far down slope side is over 5 feet. The fill was 67 stone. NOTHING has moved.

All but one of the houses we and all of my family have lived in for decades have been slab. Never had a problem with the plumbing in a slab. Friends, neighbors all in slabs and never heard of problem. I am sure they exist but they certainly have not affected the neighborhoods we and my extended family have lived in across many states.

The problem with a wood floor over a crawl space or basement is that it is a wood floor. A coworker had to rip out her bathroom floor in a very new house because the toilet leaked and rotted out the wood. The toilet seal in our city leaked. It was a pain. It was not really a problem since the house was a slab. If it was on a crawl space I am sure I would have had to rip out the floor and insulation and replaced it. If your toilet plugs and floods you get to go deal with the floor issues in the house and in the insulation in the crawlspace/basement. This happened in our city house. I had to clean up the mess but that was all.

Our floor in our country house is colored finished concrete. It was cheap and durable. If we want to put down wood, slate, tile, etc, we can. Plus, you can use the concrete as mass to help heat and cool your house.

We built a passive solar heated house. It works. It was cheap and easy to do. I would work better if we did not want to see our land and put in huge windows, i.e., holes in the walls to get the views. But we do like the view and opening the windows as much as well can so it all balances out. A passive solar house and a slab are made for each other.

If you are going to build a house you NEED to read this book, http://www.buildingsciencepress.com/Builders-Guide-to-HotHumid-Climates-P2.aspx.

The author knows his stuff. I read what he had to say on many a builders forums when he was having conversations regarding building techniques, details and materials. Our house is built according to the details in his book. He has various books specific to the climate in different areas of the country. What works in the South will not work well in the North and vice versa.

Get his book. Read it. Also read the information on the Building Science website.

Lstiburek argues for insulated and humidity controlled attics AND crawl spaces. I think he is correct. However, and he will say this, getting his details approved by a building inspector can be interesting. We did not have to worry about the crawl space since we don't have one. I would have preferred to have treated the attic so that the heat and cold did not get into the space but I did not fight that battle with the inspectors.

One problem with insulating under the roof is the effect of the heat buildup on the roofing material. The life time and installation of the roofing material can be affected. Asphalt shingles can curl and warp if there is insulation under the roof deck. You have to check with the shingle maker to see what they say.

Houses in the south generally do not have basements since we the frost line is not that deep. In my area the frost line is not even 12 inches down. The reason basements are built up north is that they have to dig down so deep for the foundation so they might as well just have a basement. The only non slab house we ever lived in had a basement since we were so far north. The basement had water issues too.

Later,
Dan

 

[20 20]

Dmccarty; Just curious how long have you been on your slab? The reason I ask is because I have known of a couple of homes that sat great for some time{20yrs} with no trouble, THEN...... all poo hits the fan? I hope you have great luck with your slab, and enjoy the fact that there are so many different routes one can take for a foundation.

My parents house has been sitting on a flat{field} rock crawl space 4+' in the ground for over 100years. Of course back then they didn't have all these so called "helpfull regs" wonder how they ever lived? I've seen this and that about how some types of construction will hold up for blank amount of years. problem is they truely DON'T know how long they'll hold up because they've only been around for X amount of years. The sales pitch is what sell BS better then anything IMO.

 

[dave1949]

Dan:
Thanks for the book reference. I would be afraid to read it and find out what I may have done wrong We have passive solar with a slab floor too. I think for a passive solar home to be worthy of the name, it will have a slab. They are made for each other. That's the reason I have a slab, but a basement would be preferable if I could get the best of both worlds IMO.

20_20: What do you mean by all goes to poop? My slab is only 3 1/2 years old, no problems, but no guarantee of future either. I do have some confidence that short of an earthquake, it will be okay.

Lots of slab problems are related to plumbing and poor drainage. Use of copper in concrete and such. My son owns a mid-60's home on a slab with radiant heat running in copper. It's a local miracle and about the only one left in the neighborhood. The rest all developed leaks long ago and switched over to forced air primarily.

My supply plumbing is PEX, well below the slab. It was the first thing that went in on top of the excavated space. It has a protective layer of sand over it, then the rock drainage bed, then styrofoam, then the slab - which I put #5 rebar in on a 14" grid. Used extra tall chairs due to the thickness of the slab which is 8" min. The supply lines come through the slab inside 1" PVC conduit sleeves beginning with a gentle sweep up.

My radiant heat plumbing is PEX in the slab. I hope it lasts, it had a pretty good history in Europe before it became common here. If it doesn't, in a passive solar home I am not going to freeze anyways.

There are older commercially constructed slabs in this area that have no or few issues. I think the construction technique is the key to the whole thing.

There is no denying though, any slab problem tends to be a big problem by comparison to a crawlspace or basement. Of course, basement floors can have a lot of the same issues as slabs., but they aren't structural and don't have plumbing typically.

If you live in a northern climate, the slab methods described by boxygen are correct. As boxygen said, slabs are/were poorly understood, consequently many were poorly built and developed cracks and tilts. That gives them somewhat of a bad name among homebuyers around here. That's hard to overcome, plus New Englanders love their basements. They will take a damp basement over no basement.

Basements are great where a deep foundation is needed to begin with, but I personally wouldn't choose a basement in an area with a high water table or sketchy drainage. Or I would elevate the entire house to account for those factors and berm the basement walls as needed. That viewpoint comes from growing up in what used to the Great Black Swamp in NW Ohio.
Dave.

 

[herd]

Actually, a slab house in these parts (or any slab structure) is more prone to termite infestation than crawl space structure. My Dad was a Pest Control Operator for 35 years and my younger brother has the business now. I have seen much termite infestation in slab. Here's what happens: most slabs are "filled and tamped" with sand, river clay, or some type of fill. The fill is not always clean and small sticks and debris can attract termites.

The debris is eaten by termites, or rots, and voids occur. In times, the voids become small hairline cracks, sometime much larger. Those cracks are the termite's entry points. Also, keyways or other types of crack management accessories become termite entry points.

In these parts, if you fill and tamp, you are guaranteeing termites. You can control it with a termite pre-treat, and then annual applications of a termiticide. Knowing this over the years, I have never built a house on a slab. I have two porches on my house, about 4' above grade. I used metal decking to suspend the floors and then poured concrete. It is a much better floor system and costs basically the same.

 

[20 20]

I am not trying to scare anyone, a properly done slab should last a long time. I believe the problem lys with poor construction methods. Friend of mine wanted to get an equity, house{double wide} was around 8-10 years. They wanted him to put block around the house 1st{instead of the skirting}. When he did this he found his slab had shifted allmost 1 foot from one end to the other{long home}. Another guy I know from down south had his house{stick built} on a slab for 20+years. Started having some plumbing issues, checked it out and found out the slab had cracked in one corner and started dropping everything. Another guy had his house{double wide} for a year toilet backed up, slab shifted messing up plumbing. There are many more of these stories but I don't want to panic or start a B fest with anyone. If you are doing a slab just make sure it is done right. Even a little shift in a slab that causes plumbing problems could easily turn out to be much worse down the road.

Foundations can be very frustrating and much of how they work relys on the ground their in. I say every situation is different and if it were me having a foundation put in, the foundation contractor better know something about the earth{dirt, sand, clay, rock, etc} AT MY BUILDING spot. Up here I can go from clay to swamp goop to sand to rock all in a very short distance. What may work for 1 would fall to pieces on 2.