|
------__ _.�- - _ __-- _ — _.
<br /> _ -- �� Si�
<br /> -- — __ ,.. 279 f �
<br /> . I .
<br /> Moi�wre in kiuilding ConstNction
<br /> " aE diHerent levele, connecting air epncea nt only eliqhtly dif- Table 3 .... Recommended Gaod Practicd° for loft
<br /> :� ferent temperaturea, leaves � path for convective air ro- � and Attic VentilalioM � �
<br /> �� tntion which will tmnsport large amounta oE weter vapor � '
<br /> ��: (mm the warmer epsce to lhe colder. I(a membrane barrier flal Rool—Slop�3 Lrchu in �s�o�n.�or bu �� , �
<br /> . � ia ueed back oi the pinaler or interior finieh, its jointa ehould Condeneation Zann I•: Total net arrn of ventilation ehould I� � ;
<br /> be mede ovor eoma xolid tmmiag member, and not between ba y,mth" dietriouted uniformly at tt�a envex plua s vapor ��J � �
<br />• . the eWde or iu eimiler placea. Usunlly a �in. lap over a bamer in th� top etory ceiling. Freo circalat�on must be � � �
<br /> 'i� (nming membar Rill meke a rufIiciently tight joint whe¢tha pmvided through all epacn. � ' p }
<br /> �Condenestion Zano II and III:Same ae tor Zana L _� ,� �
<br /> ' interior finish is spplicd. Such e kp, hoa�ever,without back- � . �
<br /> ing would not bo ndei�unta Bnrriers attached to the wnrm � - r,on6 R00%S!ap�or�r�In<hu in �s ���n.� z '1
<br /> 1 � �
<br /> eide of ineulotioa ehould form s continuous unbroken mem- Condenention 7.one I: Total net aren of at lenet 2 louvcrc on ' •=
<br /> brane over the entire inaulated aren. Fdges should be lapped � oppoeitz eides Incnted nenr the ridgo to be �/,mth" plus a l
<br /> over framing mem6ers;ende oE strips ehould be fastened by vapor bnrrier in the top etury ccilin�. @
<br />� lapping over pintes or heuders. Avoid etaplinq insulntion Conden�^.t:nn 7.ano II:Snme ventiiation ae for Zonc I. A vapor �� t
<br /> 8anges to the eides oC LLa framinq. I( thie must be done, a bnrricr in not conniJered necceanry. i
<br /> Cnndena�Lion Zone III:Snme ne(or 7.one II. }
<br /> eepsrete vapor burricr,such ss polyethylene plastic sLceting �
<br /> ehould be inslulled over the entire wall (or best results. All p(p Faol �� �
<br /> openings Eor electricnl fixtures nnd joinls nround window and �. ��� j .
<br /> dooi casings should be c:trCfully senlal. Holes accideninlly Condenention Zone I: Tatnl net nren a( ventilntion xhould be �` ? 1
<br /> mede in the barrier should be sealed. . '/wth"�vith �/,,,W^ dietributed uni(ormly nt thc euvm and � �
<br /> 2, Venlilalion af Living Spnce. The second measure listed '(emth" locnted nt the ridge with all epucee interconnrc[ed. ; ,
<br /> A vapar 6nrricr ehoald nlea ba ueed in thc [np etory cciling. , p ,
<br /> {or the control of conccaled condensntion ie ventilntion of the Condensation 7.a❑e TI:Snme ventilntian ae for%ane I. A vnpor ' �
<br /> - Louso.Thie meaSuiC is abviously necestinry as an accompani- bnrrier is not coneiJered necceenry. � l �
<br /> ment to a vapor barrier since, i(lhe Uarrier blocks entmnce Condensation '/.onc III:Samo ne(or 7.one II. HI�
<br /> i¢to the wnlls the water va or must Ue removed by other � i
<br /> � P Gohb or Nip Roo/—Wilh Oaavpanry Canhmplahd . i.
<br /> � means.No great volume of air chnnge is necessnry,howeveq ; �f � I
<br /> 8nd normal in6ltration alone is�requently xll that is�equired Condenmtion 7.one I: Total net nrea of ventilntion uhould be T j. I
<br /> - in winter wenther. '/�mth°with y�oo6h^dietributed uni(ormly at tho eavee nnd � t
<br /> The eAectivene:�v of ventilntion with outdoor air is sho�vn in '/aoth° locnted nt the ridge with all epncee interconnecteJ. , �
<br /> FSg,7,which nlso showe the amall amount of r�atcr va�or es- A°a�°r barrier ehouid nlso be ueed on the wnrm eido of the j
<br /> 1 top ull etory r.eiling, U�e dwnr[ walle, the eloping part ot V
<br /> � caping into the bnrrier�quipped, well-insuialed wnlla and the roof,and the nttic etoq�ceilinR. �!� � j
<br /> ceilinge(2IX10 sq ft)of a typicul amall dwelling,the floor being Condenmtion 7.m�e II:Snmo ne for 'Lone L ��- �
<br /> neglected. �vidently, ventilntion of :000 c(h will remove 2l �ndenxntion %one III:Sama ee for 7.ono I ezcept that n vapor . �
<br /> ]b of vapor per day with the relntive humidity at 40 perecnt, burricr ie not r,onaidcred neccesary if ineulntlou ie nmkted. �' �, (
<br /> while at the same time 1.5 Ib escapes into the structure."1'he •��u rteapoiud tlul iu m�ny unu Inomued tentllslioe mq be derinble �
<br /> Wta:vapor production (22.5 Ib) is a typicsl amouot.Double (or nummer emn(ort.For winter comfort,iveul�Uao u roaommevdad betwroo s i
<br /> gleae will be barely eate from visiblo candensntion¢e will be ���vR�o�������orouiarmtiieted•tmr.enba �'
<br /> aeen in Fig. 4, while triple glass will prevent visiblc conden- °n�re�a.r����i�a.umon�umoRuod.�e..e�e.d. �I
<br /> eation.IIy reference to Chapter 7,2000 cfh appenrs to be near 'Ths�ane nwaben mler to Fi�.9. �I
<br /> � the minimum tor alor control,and ventilution would hnve to !
<br /> be higher whe�i cookiug is done. lly refcrence to Chnpter 25 I �
<br /> iE appearv thuE usual infiltrstion will normully eupply the 3. Venfilation oJStrueWre.The third men.aure listed for tho • '
<br /> v
<br /> neceavary air chnnge,but thnL nupplementury ventil¢Liom m�y - wntroi of concealed wndensntion is ventilution of the struo- j
<br /> be necessary in kitchen nnd Inundry for prope:vapor control ture ilselL It is eliective in certain enses especinlly as a supple- �
<br /> end tor the reduction o(penks in relntive humidity thnt�5•ould ment to wnrm-side va�:or resistance which is considurnble but �
<br /> ot6envise occur in lhose areas. not o( itself tully ndequntc. Air frorn outdoors is used. The !�
<br /> venls must be shielded(rom the entrnnce ot rnin and insecfa. :i0�
<br /> ' Attics and crnwl spaces may bo considered a9 parts of tho 1� .
<br /> � o structur�, and (or these portions ventilntion is pract.icnlly a .
<br /> �° i� n e c e s v i t�.A t t i c v e n t i l n ti o n hu s lon g been an estnblished pr¢c-
<br /> 9 tice but its cliectivenesv is likely to be diminished by the
<br /> , .000 o � newer pr¢ctice of sdding insulntion tb ceiling=. Insulation re- ;� �
<br /> � g `� � quires nddcd ventilution which in turn uecessitntes ndequnte
<br /> e � insulntion. The recommended ventilntion ahoa�n in Table 3 �Ij �
<br /> Y�� ' . o" for dwcllings'"is based on such insulntion.TY e net area reier� ��:
<br /> t z� �S to the totnl o[all openin�free from obstructions.The use of '.�.;If , �
<br /> * yD$ louveca and&mesh screen (usunlly recammended) requ'ves s ,,.
<br /> �0000 � "O � ; gross erea 225 limes that listed. In Zone I of Fig.6 a ceilin6 �u
<br /> 9 e e + E vapar bnrrier is recommended [or all constructions. It ie �I
<br /> . �� y nlso necesssry thnt strny openinqs(rom wol!s into the attic, !I, � 1
<br /> r w���"�a ios uN 3 ar around n loose fitting nttic door be nvoided.The stack e�er,� ,�p �
<br /> nanc� ro r ; allows a lar�e inflow o[warm nir(rom thc d«�elling,transport-
<br /> °e � � w �e zo ze oo v � ing much vapar to a dangcr uren.\foro desireUle ventilulion I,�� ;
<br /> YNT[P �wN'IR FC�Vv[D e.vc�r�.rw«.�e YCP pAY o[ Q�e Louse can be arranged. �,.�4 •
<br /> �Vapor eard.r,1 pum�Wall and Cdlinp Ano 1000�q n����Ioi.� Crnwl spaces under dx•ellings�chere the earth ia dnmp and
<br /> uncovered requireci n high rate o( ��entilation. r1L least [our �; �
<br /> � Fip.7....Wafer Vapor Balance in a Dwellin0 openings, one ut ench wrner, ns high ss possible, should be � �,
<br /> �1t, �+'
<br /> r. `
<br /> 1 : . Yj� ?
<br /> I
<br />
|