Building a passive cellar on the cheap

[casper2096]

Hi Guys,

Over the last couple of years my collection has grown rather rapidly and i'm now at the point where my current off site storage capacity is almost full. I moved into a new house last year and am thinking about attempting to build a small passive cellar to allow me to continue to expand the collection

I have identified what i think might be a pretty good spot however i'm not the most practical minded and was hoping that some wise heads on this forum might be able to offer some guidance.

Firstly i should say that i am still planning to keep my off site facility which would be used for the odd special bottle i have plus anything under cork

The area i have identified is underneath a staircase at the back of a garage. 2 of the walls are below ground already as the house is built into a slope cut out of a sandstone shelf. The under stair area is already sealed off as i think the previous owers used it to store tools etc. The garage floor is concrete slab. I have been monitoring daily temperature and humidity for around 6 months now and temps have varied from around 12c in the middle of winter through to a maximum of 23.1 a couple of weeks ago when the outside temp was around 37c. Daily variations seem to be around 2 degrees or so. I think the worst was maybe 3.5 but that was on the 37c day

Humidity has varied quite a bit from the low 40s up into the 80s.

My rather simplistic plan was as follows

1. Install a vapour barrier of some sort
2. Glue 75mm blue board to the walls,ceiling & wooden door to provide some insulation
3. Fix some form of rubber seal around the door

As i say i'm not that practically minded and have zero experience with passive cellars and a number of questions spring to mind

1. I'd assumed that i wouldn't need to worry about humidity too much as i will only be storing wines under screwcap . i was planning to wrap bottles ins glad wrap to protect the labels. Is this assumption correct ?

2. Any idea what kind of impact i can expect the insulation to have on temps ? I know that i'm never going to get a consistent 15c but my thoughts were if i could limit the seasonal variations to around 14-20c or so plus a daily change of 2c or less than that would be acceptable for medium term storage (5-10 years)

3. Do i need to worry about ventilation ? I was thinking that i could put in some vents or drill a few holes in the door but i wasn't sure if it was necessary and if it would then adversely impact the insulation.

I know some form of A/C would be the best way to go but this is not our 'dream house' and i didn't want to sink significant dollars into something at this stage.

Any suggestions welcome (even if they are telling me that i've got it all completely wrong and i'm dreaming with what i'm trying to do )

Cheers
Chris

[Michael R]

Good luck Casper.
I've no experience, but a recent thread has loads of info
viewtopic.php?f=1&t=14068

[vovo]

With 75mm insulation and a proper seal and assuming a decent thermal mass, I believe you would be fine. I can't see the bottle temperature rising by any where near 2deg in a day. Modern esky's (with similar or less insulation to what you are proposing) keep ice for days sometimes even in direct sunlight and they have a large delta from ambient temp.

Sounds like you have got the climate to support it, we wouldn't be able to do it long term here in Brisbane, we have had a few cool days to put it into perspective. In the last 24hrs an ambient Max of 29deg and the temperature at 1m underground is a whopping 27deg.

Someone else can confirm, but if only screw cap then humidity is not an issue, place a small bucket of water in any way (will do no harm and will add to the thermal mass). I believe ventilation is not required.

[vovo]

For peace of mind though, fill up a wine bottle with water and get a temperature logger with a probe. Drill through the screw cap, feed the probe through and seal with silicone if you want then monitor the liquid temp for a few days.

[daver6]

You don't say where you live. You mention it stayed relatively cool on one 37 degree day and have only been measuring for six months. My concern would be towards the end of summer and successive very hot days. How warm might it get then.

[rens]

For peace of mind though, fill up a wine bottle with water and get a temperature logger with a probe. Drill through the screw cap, feed the probe through and seal with silicone if you want then monitor the liquid temp for a few days.

Good idea that.

[casper2096]

Thanks for the feedback guys.

I forgot to mention that i live in Sydney and am definitely planning to hold off until Mar/Apr time before making any final decisions. That way i'll have a full summers worth of temp data. I just wanted to see if i was on the right track with my thinking.

Looking at the data again then the biggest daily variation was 2.5c but that was when the ambient temperature was mid 30s. Most days it seems to be around 1.5c and that's in an open area in the corner of the garage with zero insulation so i think there is potential

Cheers
Casp

[gbader]

Casp

I reckon just go for it - 75mm insulation is pretty good (and should help slow the variations I guess), I went 25mm to try and save space

My issue was that the thermal mass of the house would see my room climb to high 20's during summer (and that would last for days), so I went with a cheap aircon - you will see if this is an issue over summer I guess

After a few months, Temp is pretty static around 18-19 (I am seeing a peak variation of nearly 2 degrees, oddly it is only slightly less for an "in bottle" measure, but that could be related to the placement of the bottle

cheers

greg