The MBV was calculated as mass change, Dm, per m2 and per DRH , based on the mean of last three cycles once dynamic equilibrium was attained. The dynamic equilibrium was considered to be attained when the change in mass, Dm , was less than 5% between the last three cycles. Two tests were carried out. During the first test, moisture buffer value of all the samples were measured as the base case samples, before adding any layers, plasters or surface treatment. During the second test, moisture buffer values of the assemblies were measured. The routinely recorded spot measurement of air velocity with a hot-wire anemometer showed that the air velocity over the surface of the samples varied between 0.15 m/s to 0.2 m/s. The sorption kinetics, the plot of moisture uptake/release versus time from which the rate of sorption can be determined, of the following assemblies was also determined during the relative humidity cycles: Assembly 1, Assembly 2_Paint, and Assembly 10_Paint.The vapour diffusion resistance factor of the samples were determined according to the British Standard BS EN 12086. The samples were initially conditioned at C temperature and % relative humidity to reach a constant mass. The specimens were placed on glass dishes containing desiccant and salt solutions for the dry cup and wet cup test, respectively.For the dry cup test, the relative humidity inside the dishes was 0% and outside the dishes was 50 %. For wet cup test,hydroponic racks the relative humidity inside the dishes was 50 % and outside the dishes was 93 %.
The test assembly was then conditioned in a climate chamber for 24 h. The differential of partial vapour pressure between ‘in the atmosphere’ and ‘in the test assembly’ drives the vapour through the specimen. The assemblies were weighed at every 24 h until five successive determinations of change in mass per unit time for each specimen was ±5% of the mean value. The vapour diffusion resistance factor, m, was calculated using Eq..The moisture buffer values of the assemblies are presented in Fig. 3 and the percentage decrease of moisture buffer value compared to the base case is presented in Fig. 4. The kinetics of sorption of some of selected samples are presented in Fig. 5. For the kinetics, sampling frequency was 1 min and the data are presented as a running average of every 30 min. An overall observation of the moisture buffer values of the assemblies indicates that the exposed Assembly 1 and Assembly 2 demonstrate ‘Excellent’ moisture buffer value whereas all other assemblies demonstrate ‘Good’ moisture buffer value. However, a higher standard deviation from the mean moisture buffer value is observed in the base case hemp lime than in the hemp-lime with lime plaster. The in homogeneous surface of the unexposed hemp-lime may lead to air gaps between the aluminium foil and the unexposed hemp-lime surfaces. This, combined with the potentially differing surface resistance due to the in homogeneity and the variation in the air velocity within the range of 0.5 m/s over the surfaces, can plausibly contribute to the variations in moisture buffer values. Once the exposed hemp-lime surface is covered with homogenous lime plaster, the standard deviation from the mean is reduced. While the decrease of 61e69% moisture buffer value from that of the base case is significant, the moisture buffer value of the assemblies are still within the range of ‘Good’ moisture buffer classes and are comparable to the moisture buffer values of the following conventional materials, as reported in the Nordtest round robin tests: exposed spruce, exposed birch panel, exposed brick, exposed laminated wood and exposed concrete.In practical applications, the inner linings of the surfaces are usually coated with paint and can influence the moisture buffering ability of the coating and therefore, of the hygroscopic layer behind it.
The impact of the application of trade emulsion paint on the surface of the assembly is presented in Fig. 3. The results show that the application of trade paint on the surface of the assemblies decrease the MBV value of Assembly 2 by 62%, Assembly 4 by 3.6%, Assembly 7 by 2.2% and increased the MBV values of Assembly 3 by 5.2%, Assembly 6 by 5.4%, Assembly 9 by 2.8% and Assembly 10 by 7.6%. Except for Assembly 2, the changes in the MBV values as a result of applying paints are not significant. The MBV value of all the painted assemblies still remains within the classification of ‘Good’ MBV as in the case of the assemblies without paint. It is plausible that the synthetic pigments of the water based emulsion paint affects the vapour permeability of lime plaster and paper backed plasterboard at different magnitudes by modifying the surface porosity of the materials. With the assumption that Assembly 2 would perform better with organic paint, clay paint was applied on the exposed surface of an unpainted Assembly 2 and the moisture buffer value was determined. The moisture buffer value was 1.87, a 54% increase from the similar assembly with trade paint.In assembly 3 to assembly 10, different layers of component materials were added to the base case assembly as stated in Table 3. The MBV values of these added materials may contribute to the MBV of the assemblies. To assess the contribution of the added materials to the MBV of the assemblies, the MBV of the following component materials were also obtained: Plasterboard , Wood Wool Board1 and Wood Wool Board2. The result is shown in Fig. 8. The contribution of plasterboard, in the assembly where plasterboard is the only added material, can be assessed by comparing the MBV values of PB and Assembly 3. It can be observed that the MBV value of Assembly 3 is 103% higher than that of the PB, confirming that the hemp-lime in the assembly is actively involved in the moisture buffering of the composite assembly. In terms of assessing the moisture activity of WWB1, it can be observed that the MBV of Assembly 8 is 20% lower than the MBV of WWB1 which implies that hemp-lime may not be fully participating in the moisture buffering of the assembly. In addition to the high MBV of WWB1, the reason for this can be partially attributed to the comparative vapour diffusion resistance factors of PB, WWB1 and hemp-lime. The vapour diffusion resistance factor of the component materials is discussed in Section 5.3.The vapour diffusion resistance factor, m, of HL, PB, WWB1, and WWB2 was determined in both dry cup and wet cup tests.
The results are shown in Fig. 10. For the dry cup test, the vapour diffusion resistance factor of PB is 69.8% higher than that of WWB1 and the vapour diffusion resistance factor of WWB1 is 172.9% higher than that of hemp-lime. For the wet cup test, the vapour diffusion resistance factor of PB is 249.3% higher than that of WWB1 and the vapour diffusion resistance factor of WWB1 is 14.3% higher than that of hemp-lime. This, combined with the effect of the thickness of PB, air layer and WWB, will potentially decrease the effective moisture penetration depth of hemp-lime and will affect the overall MBV of the assembly.The adsorption isotherms of hemp-lime, wood wool board and plasterboard were also determined by the gravimetric method using a climate chamber following the methodology presented in sub Section 4.3. For plasterboard, considerable difference is noted between the isotherms determined by DVS and gravimetric method. For the gravimetric method, both sides of the plasterboard contained paper while small samples of plasterboard without any paper backing were tested in the DVS instrument. It follows that the two methods of test are not directly comparable, as the paper lining has a high moisture sorption capacity which was not included in the DVStesting method. The density and porosity of the samples may also vary for these two methods.The ideal moisture buffer value and the moisture penetration depth of hemp-lime, WWB1, WWB2 and PB were calculated using Eqs. and , respectively. Because of the hysteresis between the relative humidity ranges of 33%e75%, vu was taken as an average of the adsorption and desorption curves. The practical moisture buffer value and the ideal moisture buffer value are presented in Fig. 13. The true moisture penetration depth and actual thickness of the materials are presented in Fig. 14. It can be observed in Fig. 14 that the moisture penetration depth of hemp-lime is smaller than the thickness of the system under test. It is plausible that the moisture buffer potential of hemp-lime will be fully utilised when the material is exposed to the relative humidity cycle. On the other hand,indoor garden table the moisture penetration depth of WWB1, WWB2 and PB are greater than their thickness in the system. It means that, while the moisture buffer value of those may not be fully utilised, moisture will penetrate through these materials to the next layer. However, the high vapour diffusion resistance factor of plasterboard will potentially affect the moisture buffer value of the lower layers. The experimental assessment of the moisture penetration depth of hemp-lime was also carried out. Two samples of hemp-lime with 7 cm and 12 cm thickness were covered in five sides with aluminium foil tape. A temperature and relative humidity sensor was placed between the lower surface and the aluminium foil tape.
The sensors were exposed to the cyclic moisture profile following the Nordtest protocol. It was observed that the amplitudes of relative humidity variation at 7 cm and 12 cm are 23.07% and 0.28%, respectively, of the amplitudes of relative humidity variation at the surface. At the true moisture penetration depth, the amplitude of variation of relative humidity should be 0.37%. When compared in terms of vapour pressure, the variations are 70% and 6% at 7 cm and 12 cm, respectively. Therefore, it is plausible that the moisture penetration depth of the formulated hemp-lime is higher than 7 cm and closer to 12 cm.2015 conference on medical use of marijuana indicated that 23 US states have legalised medical marijuana with some also legalising marijuana for recreational use. Although there is moderate evidence for efficacy of cannabinoids for chronic pain and spasticity, and some evidence for Multiple Sclerosis and treatment-resistant epilepsy, there is not good evidence for its use to treat nausea and vomiting associated with chemotherapy,perhaps the best known indication for medical marijuana. Some pregnant women report using marijuana to alleviate nausea and vomiting in pregnancy with success but evidence for its efficacy is mostly anecdotal. However, reports of adverse events for non-pregnant populations using medical marijuana raise concerns for pregnant marijuana users. According to the National Drug Strategy Household Survey in Australia, 7.6% of females aged ≥14 years used marijuana during 2010 , with 34.8% of the female population having used marijuana at least once in their lifetime. A similar trend has also been observed in New Zealand and Europe, with 47.2% of women aged ≥16 years in NZ, 24.6% in the United Kingdom and 17.5% in Ireland having used marijuana at least once. Apart from reported negative impacts on fetal growth and brain development, marijuana has been associated with adverse pregnancy outcomes, including preterm birth , small for gestational age , placental abruption and antepartum haemorrhage.
Specifically, studies have shown that using marijuana during pregnancy is associated with low birthweight and increases the risk of PTB and SGA, with an odds ratio of at least 1.5 when adjusted for age, BMI and smoking. The association between marijuana use and pregnancy outcomes is often confounded by other known risk factors including cigarette smoking, body mass index , and socioeconomic index . Women who use marijuana also tend to smoke cigarettes and are more likely to use other drugs and alcohol, for whom national statistics have shown that amongst Australian women aged ≥14years who used marijuana in 2010, 82.7% also consumed alcohol, and 68.5% were cigarette smokers, with similar patterns of prevalence in New Zealand. There have been inconsistent results reported from American prospective cohort studies, in which associations of marijuana use with adverse pregnancy outcomes were either found or not found. Hence, this study aimed to examine the association of maternal marijuana use in a multi-centre cohort with major pregnancy complications, amongst both cigarette smokers and non-smokers, controlling for well-known risk factors including age, SEI and BMI, as well as its effects on length of gestation.