How would you deal with ventilation if making an underground/dugout home or other old style building?

[Gueyog8a7]

Having lived in the van full-time about a year exactly now I have learned how important ventilation is for stopping mold and otherwise keeping the air fresh.

With the many homes I have seen build into the ground like below I wonder how ventilation would be managed.

These videos are popular and everyone fanboying for them but I wonder about the practical aspects. The guys who make the videos seem to just do it for for the youtube views and don't seem to live in them. They seem to spend as much time on making a flashy looking video as they do to making the structure itself. You only see the process of building then videos end. No talk of living in them so probably go home to their 'normal' homes after aside from the odd overnighter here and there.

Would being dug in the ground be better or worse in terms of the water it would make in the air? I am thinking it could be either. It could either be worse due to all the moisture from the ground or better as the earth would absorb the moisture like a sponge. Even if it did absorb it I wouldn't like the idea of just having raw earth as walls. I could imagine any manner of wildlife that live underground could just come in through the walls as they pleased.

In terms of insulation I was thinking building underground would be a huge advantage since the whole earth becomes your insulation right?

Most of these put wood fires but I can't stand that so think I would still use diesel/solar or just stay there in the warmer months and use van in colder times. Actually I can do without heating as never used it in winter for sleeping so just a matter of ventilation and avoiding mold. Would still have the van to go to should I want heating.

If working the land I would be out most of the day keeping warm then coming in I just dive into the bed.

What about stone age structures like these below. Would they have natural ventilation from gaps?

 

[Rocketman]

The fire is the key to keeping the moisture down. It takes a lot of “air” a moves it out the chimney - that takes the high moisture out as well. It also raises the temperature which lowers the humidity.

Without a fire I would think you would need an ERV and a de-humidifier just to start.

 

[Gueyog8a7]

The fire is the key to keeping the moisture down. It takes a lot of “air” a moves it out the chimney - that takes the high moisture out as well. It also raises the temperature which lowers the humidity.

Without a fire I would think you would need an ERV and a de-humidifier just to start.

In that case I would just use the same process I did for the van then and get a panel or two on the roof and add fans heating maybe if still wanting more but fans are much cheaper and if I don't have to heat myself then can just buy more fans.

 

[OM617YOTA]

Those videos are entertainment, not DIY advice. Made for video watch minutes, not for living in full time.

If you're really interested in this kind of thing, look up earthship homes and simple geothermal heating/cooling. Basically just blowing air through long tubes underground.

 

[Will Prowse]

Oh, this is a fantastic topic. I have been researching this myself for fun. I think a great reference is indoor shooting range ventilation. Having a hepa filter system, and a separate fan system that creates a negative pressure in the structure is ideal. And of course, cross ventilation.

After living in rv's, I learned that you want fresh air coming in where you spend most of your time, and dirty air around eating, heating and bathroom areas to be expelled outside. That cross flow of air, even when minimal (especially in extreme weathers) can make a huge difference.

If you are in a high humidity environment, a minisplit set to "dry" mode will do wonders for mold development.

 

[marionw]

Oh, this is a fantastic topic. I have been researching this myself for fun. I think a great reference is indoor shooting range ventilation. Having a hepa filter system, and a separate fan system that creates a negative pressure in the structure is ideal. And of course, cross ventilation.

After living in rv's, I learned that you want fresh air coming in where you spend most of your time, and dirty air around eating, heating and bathroom areas to be expelled outside. That cross flow of air, even when minimal (especially in extreme weathers) can make a huge difference.

If you are in a high humidity environment, a minisplit set to "dry" mode will do wonders for mold development.

First, no farting whatsoever.

The biggest issue with indoor firing ranges is lead contamination. The military is constantly dealing with this issue.

 

[Will Prowse]

First, no farting whatsoever.

The biggest issue with indoor firing ranges is lead contamination. The military is constantly dealing with this issue.

Yes exactly! The lead is a big issue.

 

[Will Prowse]

I think in most offgrid and DIY structures, moisture control is the biggest risk to health. Cross ventilation and using a minisplit as a dehumifier is best.

But if you are trying to build a true bomb shelter, indoor shooting range systems seem to be best. Especially in the case of nuclear fallout situation.

 

[Madcodger]

I keep thinking, "Just install an ERV." They're made to do exactly what you're asking: Bring in fresh air from outside, expel stale/moisture-laden/polluted air from inside. Do that while retaining as much of the heat you've already made as is possible (in winter). Don't get rid of too much moisture if that's needed inside (also winter). Do the removing (place the indoor inlet registers) from the places with the most indoor pollution (kitchens/bathrooms/etc). Do the supplying to the places in the structure where the humans rest (bedrooms/living rooms). It's literally the machine built to do what you're asking.

 

[Rednecktek]

What kind of CFM are you talking about in an indoor range? Pistol range? 100yd zero range? 250yd zero range? How many lanes? Getting all the air in one end and out the other would take some serious CFM power...

Being the guy that runs the HVAC on ships, I can tell you that a negative pressure environment is a bad idea. In a perfect world you'll want equal in and out exchange or slightly positive. Especially if you're going to have any kind of living space in there. In a negative pressure environment the air has to come from somewhere and if it's not factored in at the air handler with fresh air make-up, it'll pull from around doors (bringing unconditioned humid air into the living spaces directly) or through the drains of your sinks (bringing in bacteria laden air from the stuff growing in your drain pipes) but one way or another the air WILL get into the space.

 

[marionw]

Just go submarine (minus the nuclear reactor). A submarine's atmosphere controls handle it all while remaining submerged for months.

How Submarines Remove CO2 from their Atmospheres – Harrison's RCLII Blog

How Do You Breathe Onboard a Submarine? | Analox Group

One of the biggest challenges submariners face while on duty is how to create breathable air onboard a submarine. Find out more...

analoxgroup.com

https://www.usni.org/magazines/proceedings/1959/january/man-made-air-state-art

 

[HalfBaked]

I built my off-grid house into a hill. The back half is underground/bermed, the front half is all windows. About 1400sqft. It faces south and is wider than deep. There are sliding glass doors at each end of the house. At first I used a dehumidifier, it takes days to do any good. Eventually I found it's best to have an indoor thermometer/hygrometer with outdoor probe. Anytime the outdoor humidity is lower, I open the doors and the humidity drops in minutes.

 

[Rednecktek]

Just go submarine (minus the nuclear reactor). A submarine's atmosphere controls handle it all while remaining submerged for months.

Come on SMR's! Why skip the nuclear?

 

[Gueyog8a7]

Thanks for the replies. From the responses it sounds like the same deal as vans really then so my knowledge can just transfer over.

 

[Gueyog8a7]

Those videos are entertainment, not DIY advice. Made for video watch minutes, not for living in full time.

If you're really interested in this kind of thing, look up earthship homes and simple geothermal heating/cooling. Basically just blowing air through long tubes underground.

Indeed, that is what I insinuated in OP. Clearly they put as much or more into production value of the videos than the building.

Even so, at least with the last one, the pit house, he does seem to be going for an authentic historical structure as would have been used in that period and humans lived in them for many hundreds of years. No speaking of their general health though. Maybe they just accepted mould and such issues as part and parcel of that barbaric lifestyle.

Probably had plenty of other general risks in that time that ventilation would not have been top of their priority list.

I have spent some time with hippy types and heard they had friends/family doing similar permaculture type structures but as I was not looking to make one myself at the time I only took a passing interest. Shall take a look at your recommendations.

 

[Gueyog8a7]

I built my off-grid house into a hill. The back half is underground/bermed, the front half is all windows. About 1400sqft. It faces south and is wider than deep. There are sliding glass doors at each end of the house. At first I used a dehumidifier, it takes days to do any good. Eventually I found it's best to have an indoor thermometer/hygrometer with outdoor probe. Anytime the outdoor humidity is lower, I open the doors and the humidity drops in minutes.

I have two potential plots of land I am vying for at the moment. Have to see how things pan out but my second choice one is slightly northfacing. I know not great vs south but it isn't super steep and the land also has some on the crest of the hill and is not a really steep slope. I had been thinking about the possibilities of building like you say, half into the hill. That is one is my fallback choice though so have to see what happens.

The other, and first choice, is a nice flat plain or very slight decline generally south facing. This is better for general crop growing so would choose this one as my number 1.

 

[Partimewages]

@Rednecktek Has the correct answer. You want slightly positive inside pressure. You can only control humidity, temperature and quality by this method unless you want to invest in space station technologies.

 

[HalfBaked]

I have two potential plots of land I am vying for at the moment. Have to see how things pan out but my second choice one is slightly northfacing. I know not great vs south but it isn't super steep and the land also has some on the crest of the hill and is not a really steep slope. I had been thinking about the possibilities of building like you say, half into the hill. That is one is my fallback choice though so have to see what happens.

The other, and first choice, is a nice flat plain or very slight decline generally south facing. This is better for general crop growing so would choose this one as my number 1.

North facing will leave you cold and moldy in the dark. Southern slope or flat only.

And unless you live in an actual desert, ground tubes are mold factories with no real way to clean it. Which is why earthships are known failures outside desert areas.

 

[Gueyog8a7]

Haha, I just noti

North facing will leave you cold and moldy in the dark. Southern slope or flat only.

Yea I know, discussed that at length in a previous thread of mine as @Rednecktek may recall . In that case we were discussing very steep aspects but in this case it is not that bad.

Probably 30% approx is the crest of the hill, so would get max sun, 30% or so northern slope and 33% eastern facing. Whack the panels at the top of the hill for heating/venting power and good to go!

 

[Tulex]

Isn't this already a common issue remedied with a common air exchanger?

Like this.

 

[Gueyog8a7]

Isn't this already a common issue remedied with a common air exchanger?

Like this.

Never lived in the ground before so don't know but I guess, as mentioned, it is the same theory as vans/houses. I was just wondering if there were special considerations for this use case but now I think of it modern homes are made to be airtight aren't they for energy saving so same rules should apply.

 

[OM617YOTA]

North facing will leave you cold and moldy in the dark. Southern slope or flat only.

And unless you live in an actual desert, ground tubes are mold factories with no real way to clean it. Which is why earthships are known failures outside desert areas.

I didn't know this, interesting. Good to know!

What if ground tubes were used for heating in the winter only, so the tube walls are warmer than the air? No condensation that way.

 

[HalfBaked]

Also, make sure the roof and back of the house can take the weight and forces of gravity, including hard rain and snow load. I went with a curved (like a dam) earthbag wall in back and whole log post and beam in front and roof. Overbuild for it.

 

[HalfBaked]

I didn't know this, interesting. Good to know!

What if ground tubes were used for heating in the winter only, so the tube walls are warmer than the air? No condensation that way.

Good point, I was mostly concerned with cooling, but in the summer, the air in the tubes will be warmer than the tube wall adjacent to the earth, it will condense and make mold.

 

[OM617YOTA]

Good point, I was mostly concerned with cooling, but in the summer, the air in the tubes will be warmer than the tube wall adjacent to the earth, it will condense and make mold.

Would have to close it off during the winter. I'm envisioning something big enough to crawl through and clean, like a Jefferies tube on ST. Incredibly impractical, of course.

Better bet would probably be burying PEX or poly tubing, circulating water, using a radiator for air/water thermal exchange, and burying more tubing to make up for the efficiency loss.