Try a google image search of "stem wall" or "stem wall foundation" and see if that looks like what you're describing in your parents' house.

This one comes pretty close.
http://www.infoforbuilding.com/stemwallslab.gif

Ok then yes that kind of foundation is common in the US.

FYI Mitsubishi will be coming out with a water heater which will be tied into the exterior compressor of a mini split. The refrigerant line will go through the water heater on its way to the interior heating/cooling unit (unclear if this is 2015 or 2016). Also in 2015 they'll have the Hyper Heat models available as ducted units.

Hi Bob, Do you have any kind of web site with more info on these new Mitsubishi items.  It would make sense to get that cold air outside instead of cooling a basement that is already cold.

It looks to me like Hyper Heat is already available in one horizontally ducted model. COP is slightly higher. Now if they would only release a hydronic head in the US.

My place


I've read a lot of things of over the last months.
Ranging from opinions, to advertizing, to (bought) scientific research and often I'm not sure in what category the info falls. Not to mention contradictions and not to forget my lack of knowledge and experience.


The most recent discussion was about the thermal mass effect of walls. In that case I wonder: Assume the effect is real and significant in certain climates, will it be in my climate?




PV: Good in my climate or just to many useless days with rain, snow, fog, etc? (panels will have a free line of sight)

Solar gain glazing: Useful in my climate or would I be better of going for good U-values and/or smaller windows?

Posted By NewHoosier on 13 Feb 2015 09:29 AM
My place


I've read a lot of things of over the last months.
Ranging from opinions, to advertizing, to (bought) scientific research and often I'm not sure in what category the info falls. Not to mention contradictions and not to forget my lack of knowledge and experience.


The most recent discussion was about the thermal mass effect of walls. In that case I wonder: Assume the effect is real and significant in certain climates, will it be in my climate?




PV: Good in my climate or just to many useless days with rain, snow, fog, etc? (panels will have a free line of sight)

Solar gain glazing: Useful in my climate or would I be better of going for good U-values and/or smaller windows?

The mass effect is real enough in a humid zone 4A climate, but not a big enough effect to pay extra for on an energy-use basis, since mass walls are usually quite a bit more expensive than framed walls of equal thermal performance.

There are other valid reasons for building with concrete in Indiana beyond thermal mass.  Resistance to tornado force wind, is one:  Brick & concrete masonry unit (CMU) construction can also be mass-walls, but do not have the tornado resilience of reinforced concrete.  A direct hit by a tornado may still send your roof to Ohio or Kentucky and blow out all your windows, but the basic structure will still be there (and repairable).  Reinforced concrete walls are also a good shield against penetration by tornado-driven storm debris from your neighbor's destroyed house.

Solar gain glazing is worth while in zone 4A, but on the south side only, and only if you design in sufficient roof overhang to shade the south facing windows from mid-day sun.  Unless the windows have a soft-coat low-E coating (which would usually have to be specially ordered to get them in most zone 4 locations), any window with a U-factor of U0.35 or less typically gains more heat than it loses in winter, even if on the north side of the house.    Don't go crazy on oversizing the south facing windows (a common PassiveHouse error), since they will still get significant gain from scattered light even when shaded.  The typical window/floor area ratio of 12-15% is fine- just move most of the window area to the south side and shade them with roof overhangs (or awnings).  Even though south facing windows with roof overhangs still get direct sun in the morning & evening, the sun is an an oblique angle to the plane of the window, and most of that heat is rejected.

But east and west facing glass gets VERY direct sun in the morning & evening, with very little of that heat rejected. To limit unwanted summertime solar gain, limit the size of the windows on the east & west sides of the house, since the low sun angle in the morning & evenings can't be shaded by roof overhangs of reasonable depth.  If you MUST have windows on the west side, it's worth specifying low-gain windows, since the summertime heat gain would occur during the warmer part of the day, when the house has already been baked by the sun for many hours.

The mass effect is real enough in a humid zone 4A climate, but not a big enough effect to pay extra for on an energy-use basis, since mass walls are usually quite a bit more expensive than framed walls of equal thermal performance.

I was also thinking about the 4" interior walls. Where I live it's common the thermostat is set to 21C during daytime and at night 15C (only heating). With PV I could charge the walls during the day with free solar and let the thermal mass keep my temp fairly stable at night. The exterior walls wll be ICF so the insulation basically rules out using it for thermal mass.

There are other valid reasons for building with concrete in Indiana beyond thermal mass.  Resistance to tornado force wind, is one:  Brick & concrete masonry unit (CMU) construction can also be mass-walls, but do not have the tornado resilience of reinforced concrete.  A direct hit by a tornado may still send your roof to Ohio or Kentucky

I'll go for a concrete roof. Possibly/likely a pitched roof on it because it looks good. I worry more about my PV panels. From which direction do the tornado come? If your reference to Kentucky or Ohio wasn't just a funny remark my PV would be safe on the south side of the house. I really need to take that into account because my house likely will be in the middle of what's now a huge corn field.

and blow out all your windows, but the basic structure will still be there (and repairable).

Storm shutters. Seems like minimizing window area is wise in this case.

Reinforced concrete walls are also a good shield against penetration by tornado-driven storm debris from your neighbor's destroyed house.

All brick. And a steel sip barn.

Solar gain glazing is worth while in zone 4A, but on the south side only, and only if you design in sufficient roof overhang to shade the south facing windows from mid-day sun.

2 feet.

Unless the windows have a soft-coat low-E coating (which would usually have to be specially ordered to get them in most zone 4 locations), any window with a U-factor of U0.35 or less typically gains more heat than it loses in winter, even if on the north side of the house.

I found a 'study' geared toward the Indianapolis climate with BTU savings for all sort of changes made to a house. A quite big saver is R4 window covering for the winter night. I have no idea what that could be. It would be great if I could combine it with making my windows storm proof. Those 'rolling shutter' likely will do the the job. Very effective but ugly.

Don't go crazy on oversizing the south facing windows (a common PassiveHouse error), since they will still get significant gain from scattered light even when shaded.  The typical window/floor area ratio of 12-15% is fine- just move most of the window area to the south side and shade them with roof overhangs (or awnings).

I may even undersize. I really like sunlight. I have it in my current house but it's so irritation shining on TV and PC. I wonder that money isn't better spend on a larger PV array instead of expensive windows that need to be protected (storm) and 'managed' (curtains/shutters) etc for trouble free usage.

Even though south facing windows with roof overhangs still get direct sun in the morning & evening, the sun is an an oblique angle to the plane of the window, and most of that heat is rejected.

But east and west facing glass gets VERY direct sun in the morning & evening, with very little of that heat rejected. To limit unwanted summertime solar gain, limit the size of the windows on the east & west sides of the house, since the low sun angle in the morning & evenings can't be shaded by roof overhangs of reasonable depth.  If you MUST have windows on the west side, it's worth specifying low-gain windows, since the summertime heat gain would occur during the warmer part of the day, when the house has already been baked by the sun for many hours.

I'm busy optimizing my layout so that bathroom, pantry can act as a shield for the rooms I actually live in.

Using PV as thermal heating, unleveraged by heat pumps would be ridiculously expensive relative to other methods.

PV is never going to be safe from a direct hit from a tornado, or from flying debris from a near miss. (That's why you need insurance.)

A friend's office in Louisville Kentucky a friend's office on the 8th floor had a window broken by flying bricks stripped from other buildings by a tornado back in 1976. Your neighbor's brick can fly too- they'll break your windows, but not your ICF.

An R4 window is U0.25, can be done as a dual-pane with multiple low-E coatings and an inert gas fill and is much cheaper than an R5 or higher triple-pane. A U0.28 window is R3.6, and is still pretty good, and cheaper than a U0.25 window. The solar heat gain coefficient (SGHC) can be either very lower or in the mid-range at either U0.25 or U0.28. For east or west facing windows, low SGHC numbers are better, for south or north facing higher SGHC is better, as long as the roof overhangs properly shade the south side from mid-day summertime gain. In your climate there's no rationale for high-performance triple-panes- the money is better spent on PV.

Thermally insulating roller shutters or window covers aren't really "worth it" in your climate except as a retrofit fix to a bad house design with too much of the wrong window.

North facing windows are the best for daylighting purposes, since they are low-glare. South facing windows maximize glare except when shaded by overhangs. In mid-winter it may be "worth it" to tolerate some mid-day glare for the passive solar gain. East & west facing windows have glare that is difficult to shade with overhangs.

I was thinking about Eric's post (15 August). Especially the roof part of the picture.

My thought is a strong construction that has weaker parts to protect the rest.

The house a concrete box all around.

Big bolts are poured into the concrete walls. The main framework of the roof is fastened with it. Over that framework is some sort of covering. Tiles, shingles, etc

The roof as a whole should be able to withstand a big storm. But if things get very extrem like an F5 the roof will just blow off, but the framework will be undamaged.

The next step would be a F5 resistant roof which, I think, can only be made out of concrete or welded steel?

Let me first say I don’t know squat about building tornado proof buildings. I would probably opt for the redneck solution and buy an old VW micro bus that does not run and burry it in a hillside, or better yet, buy a used 20 ft steel shipping container, cover it with traprock/dirt and use that as a cheap storm shelter.
It seems to me the greatest likely hood of survival is to get underground, and in something that is strong enough so that it won’t collapse when a 5000-10,000 lb object falls on it.
It would be pretty difficult to repair an ICF house that had all the bricks torn off, foam torn off, roof torn off, windows blown out, etc. It might be better to have a bonfire and start over completely.

Generally, I don’t think you are going to design a house that survives a F-5 tornado, that you would actually like to live in.
I think today, the building codes can deal with hurricanes and probably earthquakes. Today buildings are required to have extensive strapping to prevent uplift and shear walls, etc. Tornado’s are a whole different kettle of fish.
Cheers,
Eric

Eric, I know almost nothing about tornado proof building either. But I do think luck comes in to play. It matters a great deal if the tornado just blows against the house or decides to dump a truck against your windows. That said I don't have the illusion it's possible to have a F5 without damage. But I *do* want reduce damage where possible. I'm not willing to go as far as building an underground house or something like that. Just reduction of damage. Maybe aim to survive an F3 or F4 with no/minor damage and stay safe in a F5 and have not so costly damage.


I'm thinking about design choices like:
- Large or small windows?

- http://aeroedgeusa.com/

- Tiles, shingles, concrete roof

- Roof bolted to ICF walls or one pour, or connecting rebar.

- Flat, gable or pyramid shaped roof?
- 4", 6" or even 8" concrete?
- Foundation type.

- Concrete porch or better wood that breaks off without putting extra stress on the main structure.
- Positioning of windows

- Smart usage of trees and walls that would in my garden anyway.

- Types of siding. I like certain siding but also like certain stucco types

- Tips for PV array

- etc







The thing is that I have no picture in my head what my house should look like besides concrete, trouble free and energy efficient. I like pitched roofs but I saw pictures of tornado proof houses with flat roofs that look quite ok.

I fully understand nobody is able to give any guarantee concerning tornado damage but statistics could be useful. Just simple stats like 90% of shingle roofs survive F3. A concrete roof comes out undamaged from 95% of the F4's

That's basically what my whole list is about. Make adjustments/choices that each make the house a few percent safer. Yeah nothing comes undamaged out of an F5 but that doesn't mean I can't try to come undamaged out of an F1-F3.....

I'd look at building a SCIP (concrete/foam/concrete) house. Then the roof is the same as the walls. You can make the concrete as thick as you want.

Structural mortar can be used instead of concrete which allows smaller equipment to be used for the spraying.

When designing for wind events, a pitched roof is better than a flat one. A metal roof is better than shingle. Outside parts of the house like porches should have independent structural members for their roof, not simply part of the main roof that continues on. And similarly really long overhangs should be avoided. Openings should be kept small when possible, for example, two separate 8 or 9 foot wide garage doors are better than one large double-wide garage door. There is much to consider, you may try starting some research at the FEMA website.

Hip roofs are supposed to handle more wind, too. In FL, we got a discount on our insurance because we had a hip roof. Flat gable ends are notoriously weak. I heavily reinforced mine, even though were aren't in an historically high wind area.

Jelly, I don't understand why 2 garage doors are better than one large one. My guess is that as soon the wind gets inside the garage the other doors will be ripped out seconds later. Or is it just that a double width door is weaker than single wide doors?




Flat vs pitched is something designers don't seem to agree upon. I've read several sites about storm proof houses and indeed several advise roof with a moderate pitch. Some say below 4/12 while others advise between 4/12 and 6/12. But site with pictures about storm proof houses show, yes you guessed it right, flat roofs :-)
The list of opinions wouldn't be complete if research shows roofs with a 65 degree pitch are the strongest of all.... http://yolandatyphoonhouse.blogspot.nl/2013_11_01_archive.html (2/5 down the page)




Personally I think flat roofs are (much) stronger that pitched roofs. BUT due being flat they experience lots more uplift forces. They aren't pushed off but literally lifted up. Not that it really matters how the roof it torn off. The effect is the same. The uplift can be halved with http://aeroedgeusa.com

One of the pictures with a storm proof house shows a flat roof that has a slope. Is that a contradiction? :-)
That slope was very moderate. My *guess* about 4/12. A major advantage is the whole roof could be filled with PV. Gable and hip roofs have far less area. I used some solar output calculators and a 4/12 pitch give very good performance. That means the panels require no racking. If they can be attached to the roof without racking, wind has far less grip on them. Which obviously is a big advantage. Unfortunately nearly flat roof means that snow doesn't slide off.

Posted By jdebree on 19 Feb 2015 06:20 AM
Hip roofs are supposed to handle more wind, too. In FL, we got a discount on our insurance because we had a hip roof. Flat gable ends are notoriously weak. I heavily reinforced mine, even though were aren't in an historically high wind area.

I guess they base that reduction on damage statistics of previous storms. On the other hand things often are based on nothing/assumptions/outdated research. Take for example that PV should be orientated south. Util companies often give rebates on properly installed PV. Part of properly is south orientation. But if you Google for something like solar west orientation you find research showing that orientating west is a very good option too. It generates far less power in total but performs good at peak times. And that's great news for the util company. Better that than people feeding the grid when they don't really need extra power.




I think internet has become too big. There are 'experts' to support any view. :-)

A double garage door is weaker than a narrower one. But the double door also has a wider opening, therefore it is more vulnerable to the wind entering.

A gable end on a wood framed structure is very weak, hence the suggestion for a hip roof. If the gable end is ICF, SIP, reinforced concrete or CMU then it's not such a concern.

You can find conflicting information all over the internet, but it's not necessary to reinvent the wheel. A flat roof just can't be stronger; the engineering has already been done on this. I would suggest that if you do some deeper reading of published material by experts, then storm design principles may make more sense to you. The forces that are involved with wind events are not as simple as they may seem.