Sick Building Syndrome? Airplane colds?

[puntloos]

My wife especially often complains about air conditioning in her office and often gets sick on airplanes, and my setup contains, well 'air conditioning'.

 

- MVHR (haven't looked at brands yet, Zehnder?)

- A2W ASHP - likely Mitsubishi Ecodan for hot water and UFH

- A2A multi-split ASHP - Mitsubishi MXZ-F range with mostly/all compact ducted FCUs in many rooms

 

Is airplane 'sickness' attributable to air conditioning? Is it 'any' AC or is a properly designed system fine? Is there stuff I can do 'now' to avoid problems? Of course a stream of constant cold dry air in your face is probably worse than a gentle stream in a highly insulated house.. but still?

 

 

 

[ProDave]

I would definitely say fit MVHR.  Apart from the energy saving aspect by ventiliating your house with little heat loss, it's other big advantage is the air is always fresh and stale smelly air constantly removed from kitchens and bathrooms.  the house never smells or feels stuffy and never has problems with condensation.

 

I would say in your case it is a must have.

[Temp]

 

6 hours ago, puntloos said:

and often gets sick on airplanes

Do you mean she gets travel sick or catches a cold? Travel sick is caused by motion. Cold symptoms take 1-3 days to appear (more normally 2-3 days). You catch colds from other people not AC systems. Although I guess office AC may help spread colds if they recycle a lot of air. Not an issue for MVHR.

 

 

Edited December 9, 2021 by Temp

[Temp]

We love our MVHR system. Air feels a lot fresher, no condensation anywhere, towels dry quickly. Only possible downside is dry air in winter but we don't find it a problem. 

[puntloos]

Yeah i have the impression MVHR will prevent any weirdness from happening. I suppose that 'bad airplane' colds (so yeah not motion sickness) are perhaps just the airplane pulling air-filled-with-farts-and-bugs into your face. Some MVHRs even have anti-scary-bug-filters, no?

[dpmiller]

are the issues humidity-related maybe?

[joth]

One thing about a.c. is it requires condensation trays, which if not perfectly installed to drain out can collect a pool of stagnant water which incoming warm air then passes over. Probably a bit of a leap to claim that causes all sickness, but still, not a desirable thing to have. 

[Seeoda]

On 09/12/2021 at 23:29, puntloos said:

Yeah i have the impression MVHR will prevent any weirdness from happening. I suppose that 'bad airplane' colds (so yeah not motion sickness) are perhaps just the airplane pulling air-filled-with-farts-and-bugs into your face. Some MVHRs even have anti-scary-bug-filters, no?

If you have a valve in the wrong location you can cause discomfort with them. Like you dont want one over a bed

[SteamyTea]

On 09/12/2021 at 15:54, puntloos said:

Is airplane 'sickness' attributable to air conditioning?

Yes and no.

There are many anecdotal reports that the dry air in an aeroplane causes cold like symptom and I have experiences a dry, cracked and bleeding inner nose after a flight to San Francisco.

Trouble is, we can all get those symptoms at any time.

But the main thing is that air at 10,000 metres is extremely dry, so the air entering the cabin is starting off with little water vapour in it, and when heated, by 70 K, is even dryer.

But then you also have up to 400 people breathing out a litre each of water on a 12 hour flight.

You can get units that introduce moisture into the air, but never heard of one in the domestic setting.  Though we did have a water tray that sat on the radiator back in the 1960s as there was a belief that central heating was bad for us.  We never filled it up.

[joth]

1 hour ago, SteamyTea said:

You can get units that introduce moisture into the air, but never heard of one in the domestic setting. 

 

More common these days maybe to use Enthalpy exchanger rather than heat exchanger (so ERV rather the [M]VHR system), to recover latent as well as sensible heat from the outgoing air.  

This is generally not needed in UK with its low altitudes and moist marine climate. However if you're heating the house via forced air (i.e. if you were using FCU) then this can dry the air out more, so using ERV can avoid further loss of air moisture.

 

 

Edited December 14, 2021 by joth

[SteamyTea]

9 minutes ago, joth said:

 ERV rather the [M]VHR system

Has anyone run the numbers to see how much extra energy is actually lost though moisture?

[joth]

1 hour ago, SteamyTea said:

Has anyone run the numbers to see how much extra energy is actually lost though moisture?

anybody that's modelled it in PHPP would have.

IIRC for us it was basically a wash. The extra latent energy recovered is mostly offset by the enthalpy exchanger being not so efficient  at recovering sensible heat. So the decision for one or other is largely driven by other criteria.

Of course that's just a model based on typical values; someone running a weed farm in Denver would get atypical efficiency results in practice.

 

 In terms of recording actual numbers... My Q350 UI gives an overall score for heat energy saved (3.7 MWh in one year) but doesn't break it down latent vs sensible.   I do log air temp, humidity and flow rate so I suppose I have what I need to calculate this.

 

 

[Dan F]

In my experience the symtoms I get from air travel are partly (if not mostly) due to 10hrs+ of drier than normal air more than anything else.

 

MVHR is fantastic, but a standard (non-enthalpy) exchanger can mean the house can be drier than without MVHR which can be a problem in some cases.  When I discussed this with our MVHR designer his view was that this was more of a problem in a large houses with low-occupancy than in smaller houses with high occupancy.  This, I assume, is due to the amount of humidy generated (by occupation) vs. amount of air moved.  We're using a enthalpy exchanger with occupancy of 4, there house isn't huge but it is quite big.

 

PHPP will actually give you % humidy for each month of the year, and it was the low projected humidy is winter months in PHPP that let to use to decide to use the enthalpy exchanger.

 

 

[puntloos]

This is great stuff - I've never heard of an enthalpy exchanger before. How much control do you have to the level of humidity? (I guess.. as long as it is 'perfect'... is that perfect level always the same for any human?)

[joe90]

My MVHR is enthalpy, only discovered it after buying it on EBay ?‍♂️, RH is never low in our build but we are in a high RH area of the country. I installed a RH “stat” to kick in boost if required (showers/cooking) but it needs resetting winter to summer. We have discussed here before using a “stat” that reads a rapid change of RH rather than a set level which I think would work better.

[Iceverge]

We're in Ireland, terrifically damp. 

Airtight with non enthalpy MVHR. 

RH typically 50-60%. 

 

Airplanes suffer from chronically low humidity. As low as 5% RH, which is a real stressor on health. I've seen a 500mm bottle water poured into a pillow in a effort to raise local humidity while sleeping on an aircraft completely dry in 90mins. 

 

The Boeing 747 was fitted with humidifiers originally to combat this but the airlines didn't like the weight so threw them out. The 777 is notoriously super dry. 

 

The humidity, cabin altitude (6-8000ft) the stress of travelling, disrupted sleep (very important), diet and dehydration put flying in a different league to domestic MVHR from a health perspective. 

 

As an alternative to ERV, MVHR with some house plants can nudge up the RH when you need it. 

[joth]

4 hours ago, joe90 said:

I installed a RH “stat” to kick in boost if required (showers/cooking) but it needs resetting winter to summer. We have discussed here before using a “stat” that reads a rapid change of RH rather than a set level which I think would work better.

 

I don't know about other brands but the Zehnder has this built in:

https://www.zehnder.co.uk/download/29630/118734/en_uk-72926.pdf

"Humidity sensors to operate the unit in response to humidity spikes above natural background humidity levels as opposed to a single threshold humidity point to activate the high set point

Humidity boost continuously monitors the humidity level within the home and looks for a man-made spike before boosting the unit, irrespective of distance or dilution"

 

I also trigger a boost when the showers or hob or oven are in use. I haven't yet worked out a boost when the cat lays a stink bomb. 

 

[Adsibob]

On 09/12/2021 at 22:22, Temp said:

Only possible downside is dry air in winter but we don't find it a problem.

I hadn’t appreciated this. I find dry air can dry my throat. Is it very noticeable and what causes it?

[Nick1c]

My understanding is that houses with a high volume of air per occupant are likely to become relatively dry with ‘standard’ MVHR , particularly in winter when the RH of the incoming air drops as it is warmed up & the moisture generated by the occupants can’t bring it back up enough. An enthalpy exchanger in some way recycles the moisture recovered from the stale air keeping things more comfortable (as a result no condensate drain is needed). 
We had one put in our Zehnder Q 350 as there are only 2 of us in the house for the vast majority of the time & if done at the time of ordering the additional cost was negligible. We live on the coast & our local weather station rarely shows the RH below 80%, the house sits around 60%. It may be a waste of time, but I get eczema which is worse when it is particularly dry so didn’t want to risk it. 
 

[Adsibob]

Hmmm. Wish I’d found out about this in my hours and hours of research. Too late now. Our Brink Flair 400 went in a month or so ago, though it’s not been commissioned yet. I think Brink do make an enthalpy version, but I had no idea what it was, and as it was slightly less efficient than the regular version.
But according to this article, it’s not really a problem in the UK, and the person the article is quoting is the person that specified the design of our system, so doubt he would have advised me to get one head I asked:

 

”“The average relative humidity in the UK is between lows of 70% and highs of 90% which is considered high, suggesting humidity recovery is not that big an issue in the UK,” Vaisey says.”

 

https://passivehouseplus.ie/news/marketplace/understanding-enthalpy-heat-exchanges-for-mvhr

Edited December 18, 2021 by Adsibob

[Temp]

21 hours ago, Adsibob said:

I hadn’t appreciated this. I find dry air can dry my throat. Is it very noticeable and what causes it?

 

Cold air can't hold as much water vapour as warm air so outside air in winter is quite dry. Many people get dry skin issues in winter. Any form of ventilation allows that dry air in to replace the warmer more humid air indoors. Its a balancing act. Not enough ventilation and you get stuffy air and condensation, too much and it can be a bit dry in winter. We turn our air flow rates up and down at different times the year.

[SteamyTea]

32 minutes ago, Temp said:

Cold air can't hold as much water vapour as warm air so outside air in winter is quite dry.

Worth reading old @Ed Davies blog about it.

https://edavies.me.uk/2017/03/vapour/

[puntloos]

On a side note I've also been trying to figure out when my windshield will be fogged up (car's perma-outside) when I have to go drive, so I can pre-heat the car (can turn on heating remotely..).. but so far I haven't quite worked out the humidity and temp and dew point correlation and the actual fogging of the windshield.

[Temp]

On 19/12/2021 at 15:55, puntloos said:

On a side note I've also been trying to figure out when my windshield will be fogged up (car's perma-outside) when I have to go drive, so I can pre-heat the car (can turn on heating remotely..).. but so far I haven't quite worked out the humidity and temp and dew point correlation and the actual fogging of the windshield.

 

I find they fog up after I get in so must be me changing the humidity that causes it. Google says..

 

"exhaled air is completely saturated with water – it contains the maximum amount of moisture, and is therefore has a relative humidity of 100%."

 

Does that suggests if the glass is colder than exhaled breath you will always get condensation?  

[onefoof]

The air in an aircraft is very dry when you are at cruising altitude.  The key is to drink far more water than you would normally do. most passengers leave the aircraft dehydrated and that is the cause of a lot of problems.